src/cli/workspace.rs at b5e98094eb8f · andymccall/oxygen

# b5e98094eb8f oxygen / src / cli / workspace.rs
98.0 KiB · Rust · last changed merge=union: a checkout keeps both sides of a union file's adjacent insertions (refs #145) 9 days ago source blame history raw
//! Commands that act on the local repository and working copy.

use super::format::{
    author_name, deps_line, deps_of, plural, short_id, signature_line, signature_mark_of,
    subject_of, via, when,
};
use super::json;
use super::open;
use super::ui;
use anyhow::Result;
use oxy_core::objects::ChangeKind;
use oxy_core::repo::SignatureStatus;
use oxy_core::repo::{render_change, ChangeStatus, Repo};
use std::io::Write;
use std::path::PathBuf;

pub fn init(path: Option<PathBuf>, bare: bool, store: Option<&str>) -> Result<i32> {
    let path = path.unwrap_or(std::env::current_dir()?);
    let repo = Repo::init_new(&path, bare, store)?;
    println!(
        "{} {}oxy repository in {}",
        ui::done("Initialized"),
        if bare { "bare " } else { "" },
        ui::path(repo.root().display())
    );
    println!(
        "{}",
        ui::kv("bookmark", ui::bookmark(&repo.config.bookmark))
    );
    if let Some(url) = &repo.config.storage_url {
        println!(
            "{}",
            ui::kv(
                "store",
                format!(
                    "{url} (cache in {}, up to {} MiB)",
                    ui::path(repo.root().join(".oxy/cache").display()),
                    repo.config.storage_cache >> 20
                )
            )
        );
    }
    println!(
        "{}",
        ui::kv(
            "author",
            format!(
                "{} <{}>",
                ui::author(&repo.config.author_name),
                repo.config.author_email
            )
        )
    );
    Ok(0)
}

fn status_tag(s: ChangeStatus) -> &'static str {
    match s {
        ChangeStatus::Added => "A",
        ChangeStatus::Modified => "M",
        ChangeStatus::Removed => "D",
        ChangeStatus::Renamed => "R",
        ChangeStatus::ModeChanged => "X",
        ChangeStatus::ConflictEdited => "C!",
        ChangeStatus::Resolved => "V",
    }
}

/// New untracked files left out of the snapshot for their size (oxygen#98):
/// named, with how to keep them out quietly or take them in.
fn print_skipped_large(repo: &Repo) {
    let skipped = repo.skipped_large();
    if skipped.is_empty() {
        return;
    }
    let size = |n: u64| {
        if n >= 1 << 30 {
            format!("{:.1} GiB", n as f64 / (1u64 << 30) as f64)
        } else {
            format!("{:.0} MiB", n as f64 / (1u64 << 20) as f64)
        }
    };
    println!();
    println!(
        "{} {}",
        ui::section(ui::warn("Not tracked")),
        ui::dim(format!("new files over {}", size(repo.config.max_new_file)))
    );
    for (p, n) in &skipped {
        println!("  {} {}  {}", ui::caution(), ui::path(p), ui::dim(size(*n)));
    }
    println!(
        "  {} {}",
        ui::note(),
        ui::dim(
            "to leave them out quietly, list them in .oxyignore; to track one, \
             raise snapshot.max-new-file-size (oxy config snapshot.max-new-file-size 2G)"
        )
    );
}

/// Name what a checkout removed from the working copy (oxygen#102): a
/// switch to a bookmark lacking files takes them off disk, which an
/// editor open on the tree notices before a person reading a count does.
fn print_removed(r: &oxy_core::repo::CheckoutReport) {
    if r.removed == 0 {
        return;
    }
    let more = r.removed.saturating_sub(r.removed_paths.len());
    let names = r.removed_paths.join(", ");
    let tail = if more > 0 {
        format!(" and {more} more")
    } else {
        String::new()
    };
    let lead = if r.removed >= 20 {
        ui::caution()
    } else {
        ui::note()
    };
    println!(
        "  {} {}",
        lead,
        ui::dim(format!(
            "removed from disk (the bookmark does not have them): {names}{tail}"
        ))
    );
}

/// Name the work a switch carried (oxygen#120): it is still on disk, as it
/// was, on the new bookmark.
fn print_carried(paths: &[String]) {
    if paths.is_empty() {
        return;
    }
    let shown: Vec<&str> = paths.iter().take(10).map(String::as_str).collect();
    let more = paths.len().saturating_sub(shown.len());
    println!(
        "  {} {}",
        ui::note(),
        ui::dim(format!(
            "carried, as they were: {}{}",
            shown.join(", "),
            if more > 0 {
                format!(" and {more} more")
            } else {
                String::new()
            }
        ))
    );
}

/// Folders holding a repository of their own, which oxy leaves out (oxygen#43):
/// named, with how to track them.
fn print_untracked_nested(repo: &Repo, nested: &[String]) {
    if nested.is_empty() {
        return;
    }
    println!();
    println!(
        "{} {}",
        ui::section(ui::warn("Not tracked")),
        ui::dim("folders holding a repository of their own")
    );
    for p in nested {
        let kind = if repo.root().join(p).join(".git").exists() {
            "Git"
        } else {
            "Oxygen"
        };
        println!(
            "  {} {}  {}",
            ui::caution(),
            ui::path(format!("{p}/")),
            ui::dim(format!("a nested {kind} repository"))
        );
    }
    println!(
        "  {} {}",
        ui::note(),
        ui::dim(
            "to track one's files, remove its .git (or .oxy); to keep it a repository of its own, \
             oxy submodule add URL PATH; to leave it out quietly, list it in .oxyignore"
        )
    );
}

/// The working copy's changed paths, or that it is clean.
fn print_statuses(statuses: &[oxy_core::repo::PathStatus]) {
    if statuses.is_empty() {
        println!(
            "  {} {}",
            ui::ok(ui::glyph("✔", "*")),
            ui::dim("nothing to commit, working copy clean")
        );
        return;
    }
    println!();
    for s in statuses {
        println!(
            "  {} {}",
            ui::status_mark(status_tag(s.status)),
            ui::path(&s.path)
        );
    }
}

/// Say when the working copy has fallen behind its own bookmark: a
/// "clean" status there hid a pull that left it on old code (oxygen#89).
fn print_behind(repo: &Repo) {
    if let Ok(Some(n)) = repo.working_copy_behind() {
        println!(
            "  {} {}",
            ui::caution(),
            ui::warn(format!(
                "the working copy is behind {}: it lacks {} the bookmark has; oxy checkout brings it up",
                repo.config.bookmark,
                plural(n, "change")
            ))
        );
    }
}

pub fn status(json: bool) -> Result<i32> {
    let repo = open()?;
    // Answered by the manifest alone, with no history to load (oxygen#35,
    // #41): a clean working copy, or one as the last snapshot left it.
    let known = if json {
        None
    } else {
        repo.status_by_manifest()?
    };
    if let Some(statuses) = known {
        let (_, wc) = repo.working_copy()?;
        let heads = repo.bookmark_heads()?;
        println!(
            "{} {}{}working copy {}{}{}",
            ui::dim("On"),
            ui::bookmark(&repo.config.bookmark),
            ui::sep(),
            ui::id(wc.change_id.short(8)),
            ui::sep(),
            ui::dim(plural(heads.len(), "head"))
        );
        print_behind(&repo);
        print_statuses(&statuses);
        print_untracked_nested(&repo, &repo.untracked_nested());
        print_skipped_large(&repo);
        return Ok(0);
    }
    let sp = ui::spinner("Snapshotting the working copy…");
    let snap = repo.snapshot_status("oxy status")?;
    let heads = {
        let _t = oxy_core::timing::phase("status: heads");
        repo.bookmark_heads()?
    };
    let _drop = oxy_core::timing::phase("status: print and drop");
    sp.clear();
    if json {
        println!("{}", repo.status_json(&snap)?);
        return Ok(if snap.base_snapshot.is_conflicted() {
            2
        } else {
            0
        });
    }
    println!(
        "{} {}{}working copy {}{}{}",
        ui::dim("On"),
        ui::bookmark(&repo.config.bookmark),
        ui::sep(),
        ui::id(snap.wc.change_id.short(8)),
        ui::sep(),
        ui::dim(plural(heads.len(), "head"))
    );
    print_behind(&repo);
    print_statuses(&snap.statuses);
    print_untracked_nested(&repo, &snap.untracked_nested);
    print_skipped_large(&repo);
    if !snap.base_snapshot.is_conflicted() {
        return Ok(0);
    }
    println!();
    println!(
        "{} {}",
        ui::section(ui::err("Conflicts")),
        ui::dim("edit the marked files, or the .oxy-conflict-N candidates, then commit")
    );
    for c in &snap.base_snapshot.tree.conflicts {
        println!("  {} tree: {c:?}", ui::err(ui::glyph("✱", "!")));
    }
    for (p, f) in &snap.base_snapshot.files {
        if f.is_conflicted() {
            let state = match snap
                .statuses
                .iter()
                .find(|s| s.path == *p)
                .map(|s| s.status)
            {
                Some(ChangeStatus::Resolved) => {
                    ui::ok(format!("{} resolved in working copy", ui::glyph("✔", "*")))
                }
                Some(ChangeStatus::ConflictEdited) => {
                    ui::warn(format!("{} markers remain", ui::glyph("‼", "!")))
                }
                _ => ui::err(format!("{} unresolved", ui::glyph("✱", "!"))),
            };
            println!("  {}  {state}", ui::path(p));
            let resolved = matches!(
                snap.statuses
                    .iter()
                    .find(|s| s.path == *p)
                    .map(|s| s.status),
                Some(ChangeStatus::Resolved)
            );
            let both = if resolved {
                0
            } else {
                snap.base.both_sides(&f.node).iter().flatten().count()
            };
            if both > 0 {
                println!(
                    "     {}",
                    ui::dim(format!(
                        "{} adjacent {}: `oxy resolve --both {p}` keeps both sides, earliest first",
                        both,
                        if both == 1 { "insertion" } else { "insertions" }
                    ))
                );
            }
        }
    }
    Ok(2)
}

pub fn commit(
    message: &str,
    depends_on: &[String],
    paths: &[String],
    interactive: bool,
    hunks: &[usize],
) -> Result<i32> {
    let repo = open()?;
    let mut deps = Vec::new();
    for d in depends_on {
        deps.push(repo.resolve_change(d)?);
    }
    let selection = if !hunks.is_empty() {
        oxy_core::repo::Selection::Hunks(hunks.to_vec())
    } else if interactive {
        let (_, hunks) = repo.hunks()?;
        if hunks.is_empty() {
            anyhow::bail!("nothing to commit: the working copy matches its base");
        }
        let hunks: Vec<_> = hunks
            .into_iter()
            .filter(|h| {
                paths.is_empty()
                    || paths.iter().any(|p| {
                        h.path == *p || h.path.starts_with(&format!("{}/", p.trim_end_matches('/')))
                    })
            })
            .collect();
        let mut chosen = Vec::new();
        let stdin = std::io::stdin();
        let mut take_rest = false;
        for (n, h) in hunks.iter().enumerate() {
            if take_rest {
                chosen.push(h.index);
                continue;
            }
            println!(
                "{} {} {}",
                ui::section(format!("hunk {} of {}", n + 1, hunks.len())),
                ui::path(&h.path),
                ui::dim(format!("(#{})", h.index))
            );
            for line in h.text.lines() {
                let styled = if line.starts_with('+') {
                    ui::ok(line)
                } else if line.starts_with('-') {
                    ui::err(line)
                } else {
                    ui::dim(line)
                };
                println!("  {styled}");
            }
            loop {
                print!(
                    "{} ",
                    ui::warn("Commit this hunk? [y]es [n]o [a]ll remaining [q]uit:")
                );
                use std::io::Write as _;
                std::io::stdout().flush()?;
                let mut answer = String::new();
                if stdin.read_line(&mut answer)? == 0 {
                    anyhow::bail!("aborted");
                }
                match answer.trim() {
                    "y" | "Y" => {
                        chosen.push(h.index);
                        break;
                    }
                    "n" | "N" | "" => break,
                    "a" | "A" => {
                        chosen.push(h.index);
                        take_rest = true;
                        break;
                    }
                    "q" | "Q" => anyhow::bail!("aborted; nothing committed"),
                    _ => continue,
                }
            }
        }
        if chosen.is_empty() {
            anyhow::bail!("no hunks chosen; nothing committed");
        }
        oxy_core::repo::Selection::Hunks(chosen)
    } else if paths.is_empty() {
        oxy_core::repo::Selection::All
    } else {
        oxy_core::repo::Selection::Paths(paths.to_vec())
    };
    let sp = ui::spinner("Committing…");
    let (h, partial) = repo.commit_selection_partial(message, &deps, &selection)?;
    // The metadata only: a first commit's change holds the whole tree.
    let meta = repo.store().get_change_meta(&h)?;
    sp.done(&format!(
        "{} {} {}  {}",
        ui::done("Committed"),
        ui::id(meta.change_id.short(8)),
        ui::hash(format!("#{}", h.short(12))),
        ui::subject(subject_of(message))
    ));
    print_untracked_nested(&repo, &repo.untracked_nested());
    print_skipped_large(&repo);
    // Only a commit that took part of the working copy leaves anything.
    if partial {
        let rest = repo.snapshot_status("oxy commit")?;
        if !rest.statuses.is_empty() {
            println!(
                "  {} {}",
                ui::note(),
                ui::dim(format!(
                    "{} left uncommitted",
                    plural(rest.statuses.len(), "path")
                ))
            );
        }
    }
    where_now(&repo);
    Ok(0)
}

pub fn blame(path: &str, json: bool) -> Result<i32> {
    let repo = open()?;
    let lines = repo.blame(path)?;
    if json {
        let items = lines.iter().map(|l| {
            format!(
                "{{\"line\":{},\"change_id\":{},\"hash\":{},\"index\":{},\"author\":{},\"when_ms\":{}}}",
                l.line,
                oxy_core::repo::json_str(&l.change_id.to_hex()),
                oxy_core::repo::json_str(&l.hash.to_hex()),
                l.index,
                oxy_core::repo::json_str(&l.author),
                l.when_ms
            )
        });
        println!("{}", oxy_core::repo::json_array(items));
        return Ok(0);
    }
    let width = lines
        .iter()
        .map(|l| l.author.chars().count())
        .max()
        .unwrap_or(0)
        .min(20);
    let digits = lines.len().to_string().len();
    let _t = oxy_core::timing::phase("blame: print");
    // Most lines share their change with many others: each change's id,
    // author and age are formatted once, and the lines go out through one
    // buffered lock on stdout.
    let mut prefix: std::collections::HashMap<oxy_core::hash::ChangeHash, String> =
        std::collections::HashMap::new();
    let bar = ui::dim(ui::glyph("│", "|"));
    let mut out = std::io::BufWriter::with_capacity(1 << 16, std::io::stdout().lock());
    for l in &lines {
        let p = prefix.entry(l.hash).or_insert_with(|| {
            let author: String = l.author.chars().take(20).collect();
            format!(
                "{} {} {}",
                ui::id(l.change_id.short(8)),
                ui::author(format!("{author:<width$}")),
                ui::dim(ui::ago(l.when_ms))
            )
        });
        let text = String::from_utf8_lossy(&l.text);
        if writeln!(
            out,
            "{p} {:>digits$}{bar} {}",
            l.line,
            text.trim_end_matches('\n')
        )
        .is_err()
        {
            // A closed pipe (blame | head): stop quietly.
            return Ok(0);
        }
    }
    let _ = out.flush();
    Ok(0)
}

fn bisect_report(repo: &Repo, step: &oxy_core::repo::BisectStep) -> Result<i32> {
    use oxy_core::repo::BisectStep::*;
    match step {
        NeedMarks { good, bad } => {
            println!(
                "{} {} {}",
                ui::note(),
                ui::dim(format!("{good} good, {bad} bad;")),
                ui::dim(if *good == 0 {
                    "mark a known-good change or bookmark: oxy bisect good CHANGE"
                } else {
                    "mark a known-bad change or bookmark: oxy bisect bad CHANGE"
                })
            );
            Ok(0)
        }
        Testing {
            heads,
            remaining,
            steps_left,
        } => {
            println!(
                "{} {} {}",
                ui::done("Testing"),
                ui::dim(format!(
                    "{} in the state under test;",
                    plural(heads.len(), "head")
                )),
                ui::dim(format!(
                    "{remaining} candidates left, about {steps_left} more steps"
                ))
            );
            println!(
                "  {} {}",
                ui::note(),
                ui::dim("run your test, then oxy bisect good | bad | skip")
            );
            Ok(0)
        }
        Found { culprit } => {
            let c = repo.store().get_change(culprit)?;
            println!(
                "{} {} {}  {}",
                ui::done("Found"),
                ui::id(short_id(&c)),
                ui::hash(format!("#{}", culprit.short(12))),
                ui::subject(subject_of(&c.message))
            );
            println!("  {} {}", ui::note(), ui::dim("the first change whose inclusion makes the state bad; oxy bisect reset to return"));
            Ok(0)
        }
        Inconclusive { candidates } => {
            println!(
                "{} {}",
                ui::caution(),
                ui::warn(format!(
                    "every remaining candidate was skipped ({}); oxy bisect reset to return",
                    plural(candidates.len(), "change")
                ))
            );
            Ok(1)
        }
    }
}

pub fn bisect_start() -> Result<i32> {
    let repo = open()?;
    repo.bisect_start()?;
    println!(
        "{} bisect; {}",
        ui::done("Started"),
        ui::dim("now: oxy bisect good CHANGE and oxy bisect bad CHANGE")
    );
    Ok(0)
}

pub fn bisect_mark(good: Option<bool>, changes: &[String]) -> Result<i32> {
    let repo = open()?;
    let mut heads = Vec::new();
    for c in changes {
        heads.extend(repo.resolve_heads(c)?);
    }
    let step = repo.bisect_mark(good, &heads)?;
    bisect_report(&repo, &step)
}

pub fn bisect_run(command: &[String]) -> Result<i32> {
    let repo = open()?;
    let step = repo.bisect_run(command)?;
    bisect_report(&repo, &step)
}

pub fn bisect_status(as_json: bool) -> Result<i32> {
    let repo = open()?;
    if as_json {
        use oxy_core::repo::BisectStep::*;
        let v = match repo.bisect_status()? {
            None => "null".to_string(),
            Some(NeedMarks { good, bad }) => json::obj([
                ("state", json::s("need-marks")),
                ("good", json::n(good)),
                ("bad", json::n(bad)),
            ]),
            Some(Testing {
                heads,
                remaining,
                steps_left,
            }) => json::obj([
                ("state", json::s("testing")),
                ("heads", json::hashes(&heads)),
                ("remaining", json::n(remaining)),
                ("steps_left", json::n(steps_left)),
            ]),
            Some(Found { culprit }) => json::obj([
                ("state", json::s("found")),
                ("culprit", json::s(&culprit.to_hex())),
            ]),
            Some(Inconclusive { candidates }) => json::obj([
                ("state", json::s("inconclusive")),
                ("candidates", json::hashes(&candidates)),
            ]),
        };
        println!("{v}");
        return Ok(0);
    }
    match repo.bisect_status()? {
        None => {
            println!("{}", ui::dim("No bisect in progress."));
            Ok(0)
        }
        Some(step) => bisect_report(&repo, &step),
    }
}

pub fn bisect_reset() -> Result<i32> {
    let repo = open()?;
    repo.bisect_reset()?;
    println!("{} bisect; working copy restored", ui::done("Reset"));
    Ok(0)
}

/// The log: one entry per change, newest first, joined by a rail. The
/// default view is the subject and a metadata line; `verbose` adds the full
/// message, dependencies, and the authenticating key.
fn signature_json(repo: &Repo, h: &oxy_core::hash::ChangeHash) -> Result<String> {
    Ok(match repo.authenticate_change(h)? {
        SignatureStatus::Unsigned => json::obj([("status", json::s("unsigned"))]),
        SignatureStatus::Valid {
            key,
            name,
            email,
            sealed,
            revoked,
        } => json::obj([
            ("status", json::s(if sealed { "sealed" } else { "signed" })),
            ("key", json::s(&key.to_hex())),
            ("name", json::s(&name)),
            ("email", json::s(&email)),
            ("revoked", json::b(revoked)),
        ]),
        SignatureStatus::Invalid(why) => {
            json::obj([("status", json::s("invalid")), ("reason", json::s(&why))])
        }
    })
}

fn log_entry_json(repo: &Repo, e: &oxy_core::repo::LogEntry) -> Result<String> {
    let c = &e.change;
    Ok(json::obj([
        ("hash", json::s(&e.hash.to_hex())),
        ("change_id", json::s(&c.change_id.to_hex())),
        ("author", json::s(&author_name(repo, c))),
        ("author_key", json::s(&c.author.to_hex())),
        (
            "via",
            match via(
                repo,
                &repo.authenticate_change_known(&e.hash, Some(c))?,
                &c.author,
            ) {
                Some(v) => json::obj([
                    ("name", json::s(&v.name)),
                    ("email", json::s(&v.email)),
                    ("key", json::s(&v.key.to_hex())),
                    ("scope", json::opt(v.scope.as_deref(), json::s)),
                    ("expires_ms", json::opt(v.expires, json::n)),
                    ("revoked", json::b(v.revoked)),
                ]),
                None => "null".to_string(),
            },
        ),
        ("when_ms", json::n(c.hlc.wall_ms)),
        ("message", json::s(&c.message)),
        ("kind", json::s(&format!("{:?}", c.kind).to_lowercase())),
        ("deps", json::hashes(&c.deps)),
        ("head", json::b(e.is_head)),
        ("working_copy", json::b(e.is_working_copy)),
        (
            "signature",
            if e.is_working_copy {
                "null".into()
            } else {
                signature_json(repo, &e.hash)?
            },
        ),
    ]))
}

/// `START,END:PATH` for `oxy log -L`.
fn parse_line_range(spec: &str) -> Result<(usize, usize, &str)> {
    let bad = || anyhow::anyhow!("-L {spec}: expected START,END:PATH, as 10,24:src/lib.rs");
    let (range, path) = spec.split_once(':').ok_or_else(bad)?;
    let (a, b) = range.split_once(',').ok_or_else(bad)?;
    Ok((
        a.trim().parse().map_err(|_| bad())?,
        b.trim().parse().map_err(|_| bad())?,
        path,
    ))
}

pub fn log(
    revset: Option<&str>,
    limit: Option<usize>,
    verbose: bool,
    path: Option<&str>,
    lines: Option<&str>,
    as_json: bool,
) -> Result<i32> {
    let repo = open()?;
    // Whether the working copy is clean and conflicted: from the manifest
    // when it proves the working copy clean, else from a snapshot.
    // The working copy as last recorded, without looking at the files (as
    // Git's log does not): whether its change holds edits, and whether its
    // base was conflicted. `oxy status` is what checks the disk.
    let conflicted = !repo.is_at_op() && repo.recorded_conflicted()?;
    let listing = oxy_core::timing::phase("log: entries");
    let entries = match (path, lines) {
        _ if revset.is_some() => repo.log_revset(revset.unwrap_or_default())?,
        (_, Some(spec)) => {
            let (first, last, p) = parse_line_range(spec)?;
            let (_, wc) = repo.working_copy()?;
            let base = repo.load_state_history(&wc.deps)?.maximal(&wc.deps);
            repo.line_history(&base, p, first, last)?
        }
        (Some(p), None) => repo.log_for_path(p)?,
        (None, None) => repo.log()?,
    };
    drop(listing);
    let _print = oxy_core::timing::phase("log: print");
    if as_json {
        let shown = limit.unwrap_or(entries.len()).min(entries.len());
        let mut items = Vec::new();
        for e in entries.iter().take(shown) {
            items.push(log_entry_json(&repo, e)?);
        }
        println!(
            "{}",
            json::obj([
                ("bookmark", json::s(&repo.config.bookmark)),
                ("total", json::n(entries.len())),
                ("changes", json::arr(items))
            ])
        );
        return Ok(0);
    }
    let total = entries.len();
    let shown = limit.unwrap_or(total).min(total);
    // Lay out a little past what is shown, so edges into the cut are drawn.
    let window: Vec<(ChangeHash, Vec<ChangeHash>)> = entries
        .iter()
        .take((shown + MAX_EDGE).min(total))
        .map(|e| (e.hash, e.change.deps.clone()))
        .collect();
    let rows = oxy_core::lanes::graph(&window, MAX_EDGE);
    // Highlight the shortest prefix that names each change: against the
    // whole log, which is what `resolve_change` searches.
    let everything;
    let all = if path.is_some() || lines.is_some() || revset.is_some() {
        everything = repo.log()?;
        &everything
    } else {
        &entries
    };
    let prefixes = oxy_core::timing::phase("log: id prefixes");
    let id_prefix = id_prefixes(
        all.iter().map(|e| e.change.change_id.0).collect(),
        entries.iter().take(shown).map(|e| e.change.change_id.0),
    );
    drop(prefixes);
    let labels = reference_labels(&repo)?;
    for (e, row) in entries.iter().take(shown).zip(&rows) {
        let c = &e.change;
        let bullet = ui::log_bullet(
            e.is_working_copy,
            e.is_head,
            e.is_working_copy && conflicted,
        );
        let id = c.change_id.to_hex();
        let n = id_prefix.get(&c.change_id.0).copied().unwrap_or(8).min(8);
        let mut head = vec![format!("{}{}", ui::id(&id[..n]), ui::dim(&id[n..8]))];
        head.push(ui::author(author_name(&repo, c)));
        head.push(ui::dim(ui::ago(c.hlc.wall_ms)));
        if let Some(names) = labels.get(&e.hash) {
            head.push(names.join(" "));
        }
        if c.kind == ChangeKind::Resolution {
            head.push(ui::warn("resolution"));
        }
        if !e.is_working_copy {
            head.push(ui::hash(format!("#{}", e.hash.short(8))));
            let status = repo.authenticate_change_known(&e.hash, Some(c))?;
            if let Some(agent) = via(&repo, &status, &c.author) {
                head.push(ui::dim(format!("via {}", agent.name)));
            }
            head.push(signature_mark_of(&status));
        }
        println!("{}{}", node_line(row, &bullet), head.join(" "));
        let subject = if e.is_working_copy && c.message.is_empty() {
            let edited = repo
                .store()
                .get_change(&e.hash)
                .is_ok_and(|w| !w.tree_ops.is_empty() || !w.edits.is_empty());
            ui::dim(if edited {
                "(working copy, uncommitted changes)"
            } else {
                "(working copy)"
            })
        } else if c.message.trim().is_empty() {
            ui::dim("(no description)")
        } else {
            subject_of(&c.message).to_string()
        };
        println!("{}{subject}", below_line(row));
        if verbose {
            let rail = continuation(row);
            if !e.is_working_copy {
                println!(
                    "{rail}{}",
                    ui::dim(format!(
                        "{} {}",
                        when(c.hlc.wall_ms),
                        signature_line(&repo, &e.hash)?
                    ))
                );
            }
            if !c.deps.is_empty() {
                println!(
                    "{rail}{} {}",
                    ui::dim(ui::glyph("↳", "->")),
                    ui::dim(deps_of(&c.deps))
                );
            }
            let body: Vec<&str> = c
                .message
                .lines()
                .skip(1)
                .skip_while(|l| l.trim().is_empty())
                .collect();
            for line in body {
                println!("{rail}  {line}");
            }
        }
    }
    if shown < total {
        if let Some(last) = rows.get(shown.saturating_sub(1)) {
            let cut: String = last
                .below
                .iter()
                .map(|c| match c {
                    Cell::Blank | Cell::Elided | Cell::JoinRight => "  ",
                    _ => "~ ",
                })
                .collect();
            if cut.trim().is_empty() {
                println!("{}", ui::dim("~"));
            } else {
                println!("{}", ui::dim(cut.trim_end()));
            }
        }
        println!(
            "{}",
            ui::dim(format!(
                "{} {} more; pass -n to see them",
                ui::glyph("…", "..."),
                total - shown
            ))
        );
    }
    Ok(0)
}

/// Rows a drawn edge may span in `oxy log`; a longer one is elided (`~`).
const MAX_EDGE: usize = 12;

use oxy_core::hash::ChangeHash;
use oxy_core::lanes::{Cell, GraphRow};

/// A graph cell, two columns wide.
fn cell(c: Cell) -> &'static str {
    match c {
        Cell::Blank => "  ",
        Cell::Line => ui::glyph("│ ", "| "),
        Cell::Elided => "~ ",
        Cell::JoinLeft => ui::glyph("├─", "|-"),
        Cell::JoinPass => ui::glyph("──", "--"),
        Cell::JoinCross => ui::glyph("┼─", "+-"),
        Cell::JoinRight => ui::glyph("╯ ", "' "),
    }
}

/// The graph part of a change's own line, its bullet in its column.
fn node_line(row: &GraphRow, bullet: &str) -> String {
    let width = row
        .passing
        .iter()
        .copied()
        .max()
        .unwrap_or(0)
        .max(row.column)
        + 1;
    let mut out = String::new();
    for c in 0..width {
        if c == row.column {
            out.push_str(bullet);
            out.push(' ');
        } else if row.passing.contains(&c) {
            out.push_str(&ui::dim(cell(Cell::Line)));
        } else {
            out.push_str("  ");
        }
    }
    out.push(' ');
    out
}

/// The graph part of the line under a change: lanes carrying on, a join,
/// or `~` for an elided edge.
fn below_line(row: &GraphRow) -> String {
    let g: String = row.below.iter().map(|c| cell(*c)).collect();
    format!("{} ", ui::dim(g))
}

/// The graph part of any further line of a change (`-v`).
fn continuation(row: &GraphRow) -> String {
    let g: String = row
        .below
        .iter()
        .map(|c| match c {
            Cell::Line | Cell::JoinLeft | Cell::JoinCross => cell(Cell::Line),
            _ => "  ",
        })
        .collect();
    format!("{} ", ui::dim(g))
}

/// For each hex ID, the length of its shortest prefix no other ID shares.
/// The shortest prefix, in hex digits, that names each of `wanted` among
/// `all`: worked out for the few shown rather than for the whole history.
fn id_prefixes(
    mut all: Vec<[u8; 16]>,
    wanted: impl Iterator<Item = [u8; 16]>,
) -> std::collections::HashMap<[u8; 16], usize> {
    all.sort_unstable();
    all.dedup();
    // Hex digits two ids share at the start.
    let common = |a: &[u8; 16], b: &[u8; 16]| {
        let bytes = a.iter().zip(b).take_while(|(x, y)| x == y).count();
        match (a.get(bytes), b.get(bytes)) {
            (Some(x), Some(y)) if x >> 4 == y >> 4 => 2 * bytes + 1,
            _ => 2 * bytes,
        }
    };
    let mut out = std::collections::HashMap::new();
    for id in wanted {
        let Ok(i) = all.binary_search(&id) else {
            continue;
        };
        let before = i.checked_sub(1).map_or(0, |j| common(&all[j], &id));
        let after = all.get(i + 1).map_or(0, |n| common(&id, n));
        out.insert(id, before.max(after) + 1);
    }
    out
}

fn unique_prefixes(ids: impl Iterator<Item = String>) -> std::collections::HashMap<String, usize> {
    let mut v: Vec<String> = ids.collect();
    v.sort();
    v.dedup();
    let common = |a: &str, b: &str| a.bytes().zip(b.bytes()).take_while(|(x, y)| x == y).count();
    let mut out = std::collections::HashMap::with_capacity(v.len());
    for i in 0..v.len() {
        let before = if i > 0 { common(&v[i - 1], &v[i]) } else { 0 };
        let after = if i + 1 < v.len() {
            common(&v[i], &v[i + 1])
        } else {
            0
        };
        out.insert(v[i].clone(), before.max(after) + 1);
    }
    out
}

/// Bookmark, remote bookmark and tag names to show beside the changes they
/// point at. A name is shown on each head of its state; one with more than
/// three heads names too much of the log to help, so it is left out (oxy
/// bookmark list shows it). A remote bookmark at the same state as the
/// local one of that name is not repeated.
fn reference_labels(repo: &Repo) -> Result<std::collections::HashMap<ChangeHash, Vec<String>>> {
    const MAX_HEADS: usize = 3;
    let view = repo.view()?;
    let mut out: std::collections::HashMap<ChangeHash, Vec<String>> = Default::default();
    let mut add = |heads: Vec<ChangeHash>, label: String| {
        if heads.len() <= MAX_HEADS {
            for h in heads {
                out.entry(h).or_default().push(label.clone());
            }
        }
    };
    for (name, st) in &view.bookmarks {
        add(repo.store().get_state(st)?.heads, ui::bookmark(name));
    }
    for (remote, bookmarks) in &view.remotes {
        for (name, st) in bookmarks {
            if view.bookmarks.get(name) == Some(st) {
                continue;
            }
            add(
                repo.store().get_state(st)?.heads,
                ui::dim(format!("{remote}/{name}")),
            );
        }
    }
    for t in repo.tags()? {
        add(t.heads.clone(), ui::warn(&t.name));
    }
    Ok(out)
}

pub fn diff(change: Option<&str>, as_json: bool) -> Result<i32> {
    let repo = open()?;
    let hash = change.map(|c| repo.resolve_change(c)).transpose()?;
    if as_json {
        let files = repo.diff_files(hash.as_ref())?;
        let items = files.iter().map(|f| {
            json::obj([
                ("path", json::s(&f.path)),
                ("kind", json::s(&f.kind)),
                ("from", json::opt(f.from.as_deref(), json::s)),
                (
                    "hunks",
                    json::arr(f.hunks.iter().map(|h| {
                        json::obj([
                            ("base_line", json::n(h.base_line)),
                            (
                                "added",
                                json::arr(
                                    h.added.iter().map(|l| json::s(&String::from_utf8_lossy(l))),
                                ),
                            ),
                            (
                                "removed",
                                json::arr(h.removed.iter().map(|(n, l)| {
                                    json::obj([
                                        ("line", json::n(*n)),
                                        ("text", json::s(&String::from_utf8_lossy(l))),
                                    ])
                                })),
                            ),
                        ])
                    })),
                ),
            ])
        });
        println!(
            "{}",
            json::obj([
                ("change", json::opt(hash, |h| json::s(&h.to_hex()))),
                ("files", json::arr(items))
            ])
        );
        return Ok(0);
    }
    match hash {
        Some(h) => {
            let c = repo.store().get_change(&h)?;
            let (base, snapshot) = repo.change_base(&c)?;
            print!("{}", render_change(&c, &base, &snapshot));
        }
        None => {
            let (wc, base, snapshot) = repo.working_copy_with_base()?;
            let text = {
                let _t = oxy_core::timing::phase("diff: render the change");
                render_change(&wc, &base, &snapshot)
            };
            print!("{text}");
            // The process ends here: freeing the base's tree and graphs
            // one by one would only cost time (about 27 ms on Linux).
            std::mem::forget((wc, base, snapshot));
        }
    }
    Ok(0)
}

pub fn cat(path: &str, change: Option<&str>) -> Result<i32> {
    let repo = open()?;
    let heads = change.map(|c| repo.resolve_heads(c)).transpose()?;
    let bytes = repo.file_at(path, heads.as_deref())?;
    use std::io::Write as _;
    std::io::stdout().write_all(&bytes)?;
    Ok(0)
}

pub fn root(as_json: bool) -> Result<i32> {
    let Ok(repo) = Repo::open(&std::env::current_dir()?) else {
        if as_json {
            println!("null");
        }
        return Ok(1);
    };
    if as_json {
        println!(
            "{}",
            json::obj([
                ("root", json::s(&repo.root().to_string_lossy())),
                ("workspace", json::s(&repo.workspace().to_hex())),
                ("bookmark", json::s(&repo.config.bookmark))
            ])
        );
    } else {
        println!("{}", repo.root().display());
    }
    Ok(0)
}

pub fn version(as_json: bool) -> Result<i32> {
    if as_json {
        println!(
            "{}",
            json::obj([
                ("version", json::s(env!("CARGO_PKG_VERSION"))),
                // What was built: a release's or install's `oxy describe`,
                // a Flow build's heads, or "local build".
                ("build", json::s(env!("OXY_BUILD_ID"))),
                ("protocol", json::n(oxy_core::protocol::PROTOCOL_VERSION)),
                ("format", json::n(2))
            ])
        );
    } else {
        println!(
            "oxy {} (repository format 2, protocol {})",
            env!("OXY_VERSION_LONG"),
            oxy_core::protocol::PROTOCOL_VERSION
        );
    }
    Ok(0)
}

pub fn discard(paths: &[String], hunks: &[usize]) -> Result<i32> {
    let repo = open()?;
    if paths.is_empty() && hunks.is_empty() {
        anyhow::bail!("name paths to restore, or --hunks to undo chosen hunks");
    }
    let mut n = 0;
    if !hunks.is_empty() {
        n += repo.discard_hunks(hunks)?;
    }
    if !paths.is_empty() {
        n += repo.discard(paths)?;
    }
    println!(
        "{} {} restored to the working copy's base",
        ui::done("Discarded"),
        plural(n, "path")
    );
    Ok(0)
}

pub fn hunks(as_json: bool) -> Result<i32> {
    let repo = open()?;
    let (_, hunks) = repo.hunks()?;
    if as_json {
        println!(
            "{}",
            json::arr(hunks.iter().map(|h| json::obj([
                ("index", json::n(h.index)),
                ("path", json::s(&h.path)),
                ("text", json::s(&h.text))
            ])))
        );
        return Ok(0);
    }
    if hunks.is_empty() {
        println!(
            "{}",
            ui::dim("No hunks: the working copy matches its base.")
        );
    }
    for h in &hunks {
        println!(
            "{} {}",
            ui::section(format!("hunk {}", h.index)),
            ui::path(&h.path)
        );
        for line in h.text.lines() {
            let styled = if line.starts_with('+') {
                ui::ok(line)
            } else if line.starts_with('-') {
                ui::err(line)
            } else {
                ui::dim(line)
            };
            println!("  {styled}");
        }
    }
    Ok(0)
}

pub fn show(change: Option<&str>, revset: Option<&str>, stat: bool, as_json: bool) -> Result<i32> {
    let repo = open()?;
    repo.snapshot_status("oxy show")?;
    let Some(r) = revset else {
        let h = repo.resolve_change(change.unwrap_or("@"))?;
        return show_one(&repo, h, as_json, false, stat);
    };
    // Several changes: a JSON array, or the changes one after another.
    let hashes = repo.revset(r)?.hashes;
    if as_json {
        print!("[");
        for (i, h) in hashes.iter().enumerate() {
            if i > 0 {
                print!(",");
            }
            show_one(&repo, *h, true, true, stat)?;
        }
        println!("]");
        return Ok(0);
    }
    if hashes.is_empty() {
        println!("{}", ui::dim(format!("No change matches {r:?}.")));
        return Ok(0);
    }
    for (i, h) in hashes.iter().enumerate() {
        if i > 0 {
            println!();
        }
        show_one(&repo, *h, false, false, stat)?;
    }
    Ok(0)
}

/// Lines added and removed in one file's diff.
fn counts(f: &oxy_core::repo::FileDiff) -> (usize, usize) {
    f.hunks
        .iter()
        .fold((0, 0), |(a, r), h| (a + h.added.len(), r + h.removed.len()))
}

/// What `--stat` prints (oxygen#119): each file the change touched, its
/// lines added and removed, then the total.
fn print_stat(files: &[oxy_core::repo::FileDiff]) {
    let width = files
        .iter()
        .map(|f| f.path.chars().count())
        .max()
        .unwrap_or(0)
        .min(60);
    let (mut added, mut removed) = (0, 0);
    for f in files {
        let (a, r) = counts(f);
        added += a;
        removed += r;
        let path = match &f.from {
            Some(from) => format!("{from} → {}", f.path),
            None => f.path.clone(),
        };
        println!(
            " {path:<width$}  {} {}  {}",
            ui::ok(format!("{:>6}", format!("+{a}"))),
            ui::err(format!("{:>6}", format!("-{r}"))),
            ui::dim(&f.kind)
        );
    }
    println!(
        " {}",
        ui::dim(format!(
            "{} changed, {added} added, {removed} removed",
            plural(files.len(), "file")
        ))
    );
}

/// One change, as `oxy show` prints it; `inline` JSON goes without its
/// newline, for an array. `stat` lists the files instead of the diff.
fn show_one(repo: &Repo, h: ChangeHash, as_json: bool, inline: bool, stat: bool) -> Result<i32> {
    let c = repo.store().get_change(&h)?;
    if as_json {
        let files = repo.diff_files(Some(&h))?;
        let heads = repo.bookmark_heads()?;
        let entry = oxy_core::repo::LogEntry {
            hash: h,
            change: oxy_core::state::ChangeMeta::of(&c),
            is_working_copy: c.kind == oxy_core::objects::ChangeKind::WorkingCopy,
            is_head: heads.contains(&h),
        };
        let mut body = log_entry_json(repo, &entry)?;
        body.pop();
        body.push_str(&format!(
            ",{}:{}}}",
            json::s("files"),
            json::arr(files.iter().map(|f| {
                let (a, r) = counts(f);
                json::obj([
                    ("path", json::s(&f.path)),
                    ("kind", json::s(&f.kind)),
                    ("from", json::opt(f.from.as_deref(), json::s)),
                    ("added", a.to_string()),
                    ("removed", r.to_string()),
                ])
            }))
        ));
        if inline {
            print!("{body}");
        } else {
            println!("{body}");
        }
        return Ok(0);
    }
    println!(
        "{} {} {}",
        ui::section("change"),
        ui::id(short_id(&c)),
        ui::hash(format!("#{h}"))
    );
    println!("{}", ui::kv("kind", format!("{:?}", c.kind).to_lowercase()));
    // Fetched but not pulled (oxygen#56): say where it is.
    if let Some(at) = repo.remote_only_location(&h)? {
        println!(
            "{}",
            ui::kv(
                "only in",
                ui::warn(format!(
                    "{at}: fetched, not yet in a local bookmark (oxy pull)"
                ))
            )
        );
    }
    let meta = oxy_core::state::ChangeMeta::of(&c);
    let status = repo.authenticate_change_known(&h, Some(&meta))?;
    println!("{}", ui::kv("author", ui::author(author_name(repo, &meta))));
    if let Some(agent) = via(repo, &status, &meta.author) {
        println!("{}", ui::kv("via", agent.line()));
    }
    println!(
        "{}",
        ui::kv(
            "date",
            format!(
                "{} {}",
                when(c.hlc.wall_ms),
                ui::dim(format!("({})", ui::ago(c.hlc.wall_ms)))
            )
        )
    );
    println!("{}", ui::kv("deps", ui::dim(deps_line(&c))));
    println!("{}", ui::kv("sig", signature_line(repo, &h)?));
    println!();
    for line in (if c.message.is_empty() {
        "(no description)"
    } else {
        &c.message
    })
    .lines()
    {
        println!("    {line}");
    }
    println!();
    if stat {
        print_stat(&repo.diff_files(Some(&h))?);
    } else {
        print!("{}", repo.describe_change(&h)?);
    }
    Ok(0)
}

pub fn checkout(changes: &[String], discard: bool, carry: bool) -> Result<i32> {
    let repo = open()?;
    // `oxy checkout BOOKMARK` is being on that bookmark, as `git checkout
    // BRANCH` is: checking its files out under another bookmark's name
    // made the next commit move the wrong bookmark (oxygen#60).
    if let [name] = changes {
        if *name != repo.config.bookmark && names_bookmark(&repo, name)? {
            drop(repo);
            return bookmark_switch(name, discard, carry);
        }
    }
    let heads = if changes.is_empty() {
        repo.bookmark_heads()?
    } else {
        let mut heads = Vec::new();
        for c in changes {
            heads.extend(repo.resolve_heads(c)?);
        }
        heads
    };
    let spec = if changes.is_empty() {
        repo.config.bookmark.clone()
    } else {
        changes.join(" ")
    };
    let sp = ui::spinner(&format!("Checking out {spec}…"));
    let command = format!("oxy checkout {spec}");
    let (r, carried) = if carry {
        repo.checkout_carry(&heads, &spec, &command)?
    } else {
        (repo.checkout(&heads, discard, &command)?, vec![])
    };
    sp.done(&format!(
        "{} on {}: {} written, {} removed{}",
        ui::done("Working copy"),
        ui::bookmark(&spec),
        plural(r.written, "file"),
        r.removed,
        if carried.is_empty() {
            String::new()
        } else {
            format!("; carried {}", plural(carried.len(), "changed path"))
        }
    ));
    print_removed(&r);
    for n in &r.notes {
        println!("  {} {n}", ui::note());
    }
    print_kept_both(&r);
    if r.conflicted {
        println!(
            "  {} {}",
            ui::caution(),
            ui::warn("this state has conflicts; see oxy status")
        );
    }
    where_now(&repo);
    Ok(0)
}

/// Union files (`merge=union`, oxygen#145) a checkout settled itself.
fn print_kept_both(r: &oxy_core::repo::CheckoutReport) {
    for k in &r.kept_both {
        println!(
            "  {} kept both sides in {} (merge=union); the next commit records it",
            ui::note(),
            ui::path(&k.path)
        );
    }
}

pub fn resolve(paths: &[String], both: bool, reverse: bool, as_json: bool) -> Result<i32> {
    let repo = open()?;
    let mut snap = repo.snapshot("oxy resolve")?;
    let paths: Vec<String> = paths
        .iter()
        .map(|p| p.trim_start_matches("./").trim_end_matches('/').to_string())
        .collect();
    if both {
        // Adjacent insertions (oxygen#121): every side kept, in order.
        let kept = repo.keep_both(&snap, &paths, reverse)?;
        if !as_json {
            for k in &kept {
                if !k.settled.is_empty() {
                    let n: Vec<String> = k.settled.iter().map(|n| n.to_string()).collect();
                    println!("kept both  {}: conflict {}", k.path, n.join(", "));
                }
                for (n, why) in &k.left {
                    println!("markers    {}: conflict {n}: {why}", k.path);
                }
            }
        }
        snap = repo.snapshot("oxy resolve")?;
    } else if !paths.is_empty() {
        // A replace conflict has no markers to edit out: the user says which
        // content wins (oxygen#140, spec §9.3), and the snapshot builds it.
        repo.choose_resolutions(&snap.base_snapshot, &paths)?;
        snap = repo.snapshot("oxy resolve")?;
    }
    if as_json {
        println!("{}", repo.status_json(&snap)?);
        return Ok(if snap.base_snapshot.is_conflicted() {
            2
        } else {
            0
        });
    }
    if !snap.base_snapshot.is_conflicted() {
        println!("The working copy's base has no conflicts.");
        return Ok(0);
    }
    let mut remaining = 0;
    for (p, f) in &snap.base_snapshot.files {
        if !f.is_conflicted() {
            continue;
        }
        match snap
            .statuses
            .iter()
            .find(|s| s.path == *p)
            .map(|s| s.status)
        {
            Some(ChangeStatus::Resolved) => println!("resolved   {p}"),
            Some(ChangeStatus::ConflictEdited) => {
                remaining += 1;
                println!("markers    {p}");
            }
            _ => {
                remaining += 1;
                println!("unresolved {p}");
            }
        }
    }
    for c in &snap.base_snapshot.tree.conflicts {
        remaining += 1;
        println!("tree       {c:?}");
    }
    if remaining == 0 {
        println!("All conflicts are resolved; `oxy commit` will record the resolution.");
        Ok(0)
    } else {
        Ok(2)
    }
}

pub fn undo() -> Result<i32> {
    let repo = open()?;
    let u = repo.undo()?;
    println!("{} {}", ui::done("Undone:"), u.command);
    for c in &u.changes {
        println!("  {} {}", ui::note(), change_words(&repo, c));
    }
    if u.others_kept > 0 {
        let s = if u.others_kept == 1 { "" } else { "s" };
        println!(
            "  {} {}",
            ui::note(),
            ui::dim(format!(
                "{} newer operation{s} from other workspaces left as they are",
                u.others_kept
            ))
        );
    }
    for (bookmark, remote) in &u.pushed {
        println!(
            "  {} {}",
            ui::caution(),
            ui::warn(format!(
                "{remote}/{bookmark} already has what this undid: undone here only; the next push of {bookmark} needs --force to take it back there"
            ))
        );
    }
    where_now(&repo);
    Ok(0)
}

pub fn op_log(limit: Option<usize>, as_json: bool) -> Result<i32> {
    let repo = open()?;
    let ops = repo.op_log()?;
    // What each operation changed, against the one before it.
    let changes_of = |i: usize| -> Result<Vec<oxy_core::repo::ViewChange>> {
        match ops.get(i + 1) {
            Some((_, before)) => Ok(repo.view_changes(&before.view, &ops[i].1.view)?),
            None => Ok(vec![]),
        }
    };
    if as_json {
        let mut items = Vec::new();
        for (i, (r, op)) in ops.iter().enumerate().take(limit.unwrap_or(usize::MAX)) {
            let summary: Vec<String> = changes_of(i)?
                .iter()
                .map(|c| change_words(&repo, c))
                .collect();
            items.push(json::obj([
                ("id", json::s(&r.to_hex())),
                ("when_ms", json::n(op.hlc.wall_ms)),
                ("command", json::s(&op.command)),
                ("snapshot", json::b(op.is_snapshot())),
                ("current", json::b(i == 0)),
                ("changes", json::arr(summary.iter().map(|x| json::s(x)))),
            ]));
        }
        println!("{}", json::arr(items));
        return Ok(0);
    }
    let id_prefix = unique_prefixes(ops.iter().map(|(r, _)| r.to_hex()));
    let id = |r: &oxy_core::hash::ObjectRef| {
        let hex = r.to_hex();
        let n = id_prefix.get(&hex).copied().unwrap_or(12).min(12);
        format!("{}{}", ui::id(&hex[..n]), ui::dim(&hex[n..12]))
    };
    let rail = ui::dim(ui::glyph("│", "|"));
    let (mut i, mut shown) = (0, 0);
    while i < ops.len() && shown < limit.unwrap_or(usize::MAX) {
        let (r, op) = &ops[i];
        let bullet = if i == 0 {
            ui::ok(ui::glyph("@", "@"))
        } else {
            ui::dim(ui::glyph("○", "o"))
        };
        // A run of snapshots folds into one entry.
        let mut run = 1;
        while op.is_snapshot() && i + run < ops.len() && ops[i + run].1.is_snapshot() {
            run += 1;
        }
        let when = ui::dim(ui::ago(op.hlc.wall_ms));
        if op.is_snapshot() {
            let span = if run > 1 {
                format!("{} {}", ui::dim("…"), id(&ops[i + run - 1].0))
            } else {
                String::new()
            };
            println!(
                "{bullet}  {}{} {when}",
                id(r),
                if span.is_empty() {
                    String::new()
                } else {
                    format!(" {span}")
                }
            );
            println!(
                "{rail}  {}",
                ui::dim(if run == 1 {
                    "working-copy snapshot".to_string()
                } else {
                    format!("{run} working-copy snapshots")
                })
            );
        } else {
            println!("{bullet}  {} {when}", id(r));
            let words: Vec<String> = changes_of(i)?
                .iter()
                .map(|c| change_words(&repo, c))
                .collect();
            let summary = if words.is_empty() {
                if i + 1 == ops.len() {
                    "created the repository".to_string()
                } else {
                    "no bookmark or working-copy change".to_string()
                }
            } else {
                words.join("; ")
            };
            println!(
                "{rail}  {}",
                if i == 0 {
                    ui::subject(&summary)
                } else {
                    summary
                }
            );
            let cmd = op.command.lines().next().unwrap_or("");
            let cmd: String = cmd.chars().take(100).collect();
            println!("{rail}  {}", ui::dim(cmd));
        }
        i += run;
        shown += 1;
    }
    if i < ops.len() {
        println!(
            "{}",
            ui::dim(format!(
                "{} {} older; pass -n to see more",
                ui::glyph("…", "..."),
                plural(ops.len() - i, "operation")
            ))
        );
    }
    Ok(0)
}

/// One change an operation made, in words.
fn change_words(repo: &Repo, c: &oxy_core::repo::ViewChange) -> String {
    use oxy_core::repo::ViewChange::*;
    match c {
        BookmarkCreated { name, heads } => {
            format!("created bookmark {name} ({})", plural(*heads, "head"))
        }
        BookmarkDeleted { name } => format!("deleted bookmark {name}"),
        BookmarkMoved { name, from, to } if from == to => format!("moved {name}"),
        BookmarkMoved { name, from, to } => format!(
            "{name}: {from} {} {}",
            ui::glyph("→", "->"),
            plural(*to, "head")
        ),
        RemoteMoved { remote, name } => format!("{remote}/{name} updated"),
        TagCreated { name } => format!("tagged {name}"),
        TagDeleted { name } => format!("removed tag {name}"),
        Policy => "trust policy changed".to_string(),
        WorkingCopy { change } => match repo.store().get_change_meta(change) {
            Ok(m) => format!("working copy now {}", m.change_id.short(8)),
            Err(_) => "working copy moved".to_string(),
        },
    }
}

pub fn op_restore(op: &str, discard: bool) -> Result<i32> {
    let repo = open()?;
    let sp = ui::spinner(&format!("Restoring to operation {op}…"));
    let r = repo.op_restore(op, discard)?;
    sp.done(&format!(
        "{} to operation {} {}",
        ui::done("Restored"),
        ui::hash(r.op.short(12)),
        ui::dim(r.command.lines().next().unwrap_or(""))
    ));
    println!(
        "  {} {}",
        ui::note(),
        ui::dim(format!(
            "{} written, {} removed; oxy undo goes back again",
            plural(r.checkout.written, "file"),
            r.checkout.removed
        ))
    );
    where_now(&repo);
    Ok(0)
}

pub fn op_revert(op: &str) -> Result<i32> {
    let repo = open()?;
    let r = repo.op_revert(op)?;
    let view = repo.view()?;
    let names: Vec<String> = r
        .reverted
        .iter()
        .map(|n| {
            if view.bookmarks.contains_key(n) {
                ui::bookmark(n)
            } else {
                format!("{} (removed)", ui::bookmark(n))
            }
        })
        .collect();
    println!(
        "{} operation {} {}",
        ui::done("Reverted"),
        ui::hash(r.op.short(12)),
        ui::dim(r.command.lines().next().unwrap_or(""))
    );
    println!(
        "  {} {}",
        ui::note(),
        ui::dim(format!("as before it: {}", names.join(", ")))
    );
    if !r.kept.is_empty() {
        println!(
            "  {} {}",
            ui::caution(),
            ui::warn(format!(
                "left as they are, having moved again since: {}",
                r.kept.join(", ")
            ))
        );
    }
    if !r.checked_out && r.reverted.contains(&repo.config.bookmark) {
        println!(
            "  {} {}",
            ui::note(),
            ui::dim("the working copy has work of its own: oxy checkout to move it")
        );
    }
    where_now(&repo);
    Ok(0)
}

/// Where the working copy and bookmark are now, after a command moved
/// them (as jj says "Working copy now at").
pub fn where_now(repo: &Repo) {
    let Ok((_, wc)) = repo.working_copy() else {
        return;
    };
    let heads = repo.bookmark_heads().unwrap_or_default();
    let newest = heads
        .iter()
        .filter_map(|h| repo.store().get_change_meta(h).ok().map(|m| (m, *h)))
        .max_by_key(|(m, _)| m.hlc);
    println!(
        "  {} {}",
        ui::dim(format!("{:<13}", "Working copy")),
        ui::id(wc.change_id.short(8))
    );
    let tail = match newest {
        Some((m, _)) => format!(
            ", newest {} {}",
            ui::id(m.change_id.short(8)),
            subject_of(&m.message)
        ),
        None => String::new(),
    };
    println!(
        "  {} {}: {}{tail}",
        ui::dim(format!("{:<13}", "Bookmark")),
        ui::bookmark(&repo.config.bookmark),
        plural(heads.len(), "head")
    );
}

pub fn gc(now: bool, expire_snapshots: bool) -> Result<i32> {
    let mut repo = open()?;
    if expire_snapshots {
        repo.config.snapshot_retention_days = 0;
    }
    let sp = ui::spinner("Packing and pruning…");
    let r = repo.gc_with(now, &mut |phase| sp.set(&format!("{phase}…")))?;
    sp.clear();
    if r.packed.objects > 0 {
        println!(
            "Packed {} into one pack: {} bytes -> {} bytes ({:.0}%).",
            plural(r.packed.objects, "object"),
            r.packed.raw_bytes,
            r.packed.packed_bytes,
            100.0 * r.packed.packed_bytes as f64 / r.packed.raw_bytes.max(1) as f64
        );
    }
    println!(
        "{} reachable; pruned {} ({} bytes){}{}; {} present.",
        plural(r.reachable, "object"),
        plural(r.pruned.objects, "unreachable object"),
        r.pruned.bytes,
        if r.pruned.deferred > 0 {
            format!(
                "; {} deferred by the grace period (use --now)",
                plural(r.pruned.deferred, "object")
            )
        } else {
            String::new()
        },
        if r.merged_packs > 0 {
            format!("; merged {} into one", plural(r.merged_packs, "pack"))
        } else {
            String::new()
        },
        plural(repo.store().pack_count(), "pack")
    );
    // What earlier repacks replaced stays an hour for readers still using
    // it (oxygenhub#249); a collection after that deletes it.
    let kept = if r.retired.kept > 0 {
        format!(
            "{} retired less than an hour ago kept for readers",
            plural(r.retired.kept, "file")
        )
    } else {
        String::new()
    };
    if r.retired.packs + r.retired.loose > 0 {
        println!(
            "Deleted {} and {} retired by earlier repacks{}.",
            plural(r.retired.packs, "pack"),
            plural(r.retired.loose, "loose object"),
            if kept.is_empty() {
                String::new()
            } else {
                format!("; {kept}")
            }
        );
    } else if !kept.is_empty() {
        println!("{kept}.");
    }
    Ok(0)
}

/// `oxy gc --remote NAME`: fold a store remote's bundles into one.
pub fn gc_remote(name: &str, now: bool) -> Result<i32> {
    let repo = open()?;
    let sp = ui::spinner(&format!("Folding {name}'s bundles…"));
    let r = repo.gc_remote(name, now)?;
    sp.clear();
    if r.merged > 0 {
        println!(
            "{} {} into one of {} bytes ({})",
            ui::done("Folded"),
            plural(r.merged, "bundle"),
            r.bundle_bytes,
            plural(r.changes, "change")
        );
    } else {
        println!(
            "{} {}",
            ui::note(),
            ui::dim("nothing to fold: one bundle holds everything")
        );
    }
    println!(
        "  {} {}",
        ui::note(),
        ui::dim(format!(
            "removed {}{}",
            plural(r.deleted, "superseded bundle"),
            if r.deferred > 0 {
                format!(
                    "; {} kept for readers that may still fetch them (use --now)",
                    plural(r.deferred, "bundle")
                )
            } else {
                String::new()
            }
        ))
    );
    Ok(0)
}

/// `oxy doctor`: exit 1 when a check fails, 0 otherwise (warnings allowed).
pub fn doctor(offline: bool, as_json: bool) -> Result<i32> {
    use oxy_core::repo::Health;
    let repo = open()?;
    let sp = ui::spinner(if offline {
        "Checking…"
    } else {
        "Checking, and contacting remotes…"
    });
    let r = repo.doctor(!offline);
    sp.clear();
    let code = if r.worst() == Health::Fail { 1 } else { 0 };
    let word = |h: Health| match h {
        Health::Ok => "ok",
        Health::Warn => "warning",
        Health::Fail => "fail",
    };
    if as_json {
        let checks: Vec<String> = r
            .checks
            .iter()
            .map(|c| {
                json::obj([
                    ("area", json::s(&c.area)),
                    ("health", json::s(word(c.health))),
                    ("message", json::s(&c.message)),
                    ("hint", json::opt(c.hint.as_deref(), json::s)),
                ])
            })
            .collect();
        println!(
            "{}",
            json::obj([("ok", json::b(code == 0)), ("checks", json::arr(checks))])
        );
        return Ok(code);
    }
    let mut last = "";
    for c in &r.checks {
        if c.area != last {
            println!("{}", ui::section(&c.area));
            last = &c.area;
        }
        let mark = match c.health {
            Health::Ok => ui::ok(ui::glyph("✔", "v")),
            Health::Warn => ui::caution(),
            Health::Fail => ui::err(ui::glyph("✖", "x")),
        };
        println!("  {mark} {}", c.message);
        if let Some(h) = &c.hint {
            println!("    {} {}", ui::dim("→"), ui::dim(h));
        }
    }
    let fails = r.checks.iter().filter(|c| c.health == Health::Fail).count();
    let warns = r.checks.iter().filter(|c| c.health == Health::Warn).count();
    if fails + warns == 0 {
        println!("{}", ui::done("Everything looks right."));
    } else {
        println!(
            "{} {}, {}.",
            if fails > 0 {
                ui::err(ui::glyph("✖", "x"))
            } else {
                ui::caution()
            },
            plural(fails, "problem"),
            plural(warns, "warning")
        );
    }
    Ok(code)
}

/// `oxy fsck`: exit 0 when sound (warnings allowed), 1 on any error.
pub fn fsck(as_json: bool) -> Result<i32> {
    use oxy_core::repo::Severity;
    let repo = open()?;
    let sp = ui::spinner("Checking every object…");
    let r = repo.fsck()?;
    sp.clear();
    let code = if r.errors() > 0 { 1 } else { 0 };
    if as_json {
        let problems: Vec<String> = r
            .problems
            .iter()
            .map(|p| {
                json::obj([
                    (
                        "severity",
                        json::s(match p.severity {
                            Severity::Error => "error",
                            Severity::Warning => "warning",
                        }),
                    ),
                    (
                        "object",
                        json::opt(p.object.map(|o| o.to_hex()).as_deref(), json::s),
                    ),
                    ("what", json::s(&p.what)),
                ])
            })
            .collect();
        println!(
            "{}",
            json::obj([
                ("ok", json::b(code == 0)),
                ("objects", json::n(r.objects)),
                ("ops", json::n(r.ops)),
                ("changes", json::n(r.changes)),
                ("signed", json::n(r.signed)),
                ("unsigned", json::n(r.unsigned)),
                ("checkpoints", json::n(r.checkpoints)),
                ("attestations", json::n(r.attestations)),
                ("errors", json::n(r.errors())),
                ("warnings", json::n(r.warnings())),
                ("problems", json::arr(problems)),
            ])
        );
        return Ok(code);
    }
    println!(
        "Checked {}, {}, {} ({} signed or sealed, {} unsigned), {}, {}.",
        plural(r.objects, "object"),
        plural(r.ops, "operation"),
        plural(r.changes, "change"),
        r.signed,
        r.unsigned,
        plural(r.checkpoints, "checkpoint"),
        plural(r.attestations, "attestation"),
    );
    for p in &r.problems {
        let obj = p
            .object
            .map(|o| format!("{} ", ui::hash(format!("#{}", o.short(12)))))
            .unwrap_or_default();
        match p.severity {
            Severity::Error => println!("{} {obj}{}", ui::err(ui::glyph("✖", "x")), p.what),
            Severity::Warning => println!("{} {obj}{}", ui::caution(), p.what),
        }
    }
    if r.problems.is_empty() {
        println!("{}", ui::done("No problems found."));
    } else if code == 0 {
        println!(
            "{}",
            ui::done(format!("Sound, with {}.", plural(r.warnings(), "warning")))
        );
    } else {
        println!(
            "{} {} and {}. Fetch missing objects from a remote with `oxy pull`, or clone afresh and compare.",
            ui::err(ui::glyph("✖", "x")),
            plural(r.errors(), "error"),
            plural(r.warnings(), "warning")
        );
    }
    Ok(code)
}

/// The head the working copy sits on, for commands that default to it. With
/// several heads beneath the working copy, the most recently made one is
/// chosen and announced.
fn current_head(repo: &Repo) -> Result<oxy_core::hash::ChangeHash> {
    let snap = repo.snapshot_status("oxy")?;
    let base = snap.base.maximal(&snap.wc.deps);
    match base.as_slice() {
        [] => anyhow::bail!("the working copy sits on no change yet"),
        [h] => Ok(*h),
        many => {
            let latest = many
                .iter()
                .max_by_key(|h| snap.base.get(h).map(|c| (c.hlc, **h)))
                .copied()
                .unwrap();
            let c = repo.store().get_change(&latest)?;
            println!(
                "Defaulting to {} #{} (most recent of the {} heads under the working copy)",
                short_id(&c),
                latest.short(12),
                many.len()
            );
            Ok(latest)
        }
    }
}

/// `oxy describe` without -m: the working copy's name for a build.
pub fn describe_name(as_json: bool) -> Result<i32> {
    let repo = open()?;
    let d = repo.describe_working_copy()?;
    if as_json {
        println!(
            "{}",
            json::obj([
                ("describe", json::s(&d.line())),
                ("tag", json::opt(d.tag.as_ref(), |t| json::s(t))),
                ("distance", json::n(d.distance)),
                ("bookmark", json::s(&d.bookmark)),
                ("change", json::s(&d.change.to_hex())),
                ("hash", json::s(&d.hash.to_hex())),
                ("dirty", json::b(d.dirty)),
            ])
        );
    } else {
        println!("{}", d.line());
    }
    Ok(0)
}

pub fn describe(message: &str, change: Option<&str>) -> Result<i32> {
    let repo = open()?;
    let h = match change {
        Some(c) => repo.resolve_change(c)?,
        None => current_head(&repo)?,
    };
    let new = repo.describe(&h, message)?;
    let c = repo.store().get_change_meta(&new)?;
    println!(
        "{} {} {}  {}",
        ui::done("Described"),
        ui::id(c.change_id.short(8)),
        ui::hash(format!("#{}", new.short(12))),
        ui::subject(subject_of(message))
    );
    Ok(0)
}

pub fn amend(message: Option<&str>, into: Option<&str>, paths: &[String]) -> Result<i32> {
    let repo = open()?;
    let before = repo.view()?;
    let new = match into {
        Some(spec) => {
            let target = repo.resolve_change(spec)?;
            repo.amend_into(&target, message)?
        }
        None if !paths.is_empty() => repo.amend_paths(message, paths)?,
        None => repo.amend(message)?,
    };
    let c = repo.store().get_change_meta(&new)?;
    println!(
        "{} {} {}  {}",
        ui::done("Amended"),
        ui::id(c.change_id.short(8)),
        ui::hash(format!("#{}", new.short(12))),
        ui::subject(subject_of(&c.message))
    );
    // Rewriting what a remote already has means the next push replaces it
    // there (oxygen#99): say so now, not when the push is refused.
    let bookmark = repo.config.bookmark.clone();
    let (had, has) = (
        repo.heads_of(&before, &bookmark)?,
        repo.heads_of(&repo.view()?, &bookmark)?,
    );
    for (remote, bookmarks) in &before.remotes {
        let Some(st) = bookmarks.get(&bookmark) else {
            continue;
        };
        let theirs = repo.store().get_state(st)?.heads;
        if theirs.iter().any(|h| had.contains(h) && !has.contains(h)) {
            println!(
                "  {} {}",
                ui::caution(),
                ui::warn(format!(
                    "{remote}/{bookmark} has the change as it was: the next push of {bookmark} needs --force to replace it"
                ))
            );
        }
    }
    where_now(&repo);
    Ok(0)
}

pub fn abandon(change: Option<&str>, revset: Option<&str>, yes: bool) -> Result<i32> {
    let repo = open()?;
    let Some(r) = revset else {
        let h = repo.resolve_change(change.unwrap_or_default())?;
        abandon_one(&repo, h)?;
        where_now(&repo);
        return Ok(0);
    };
    // A revset: say what it selects, refuse an empty set, ask above a few.
    let selected = repo.revset(r)?;
    let wc = repo.working_copy().ok().map(|(h, _)| h);
    let hashes: Vec<ChangeHash> = selected
        .hashes
        .iter()
        .copied()
        .filter(|h| Some(*h) != wc)
        .collect();
    if hashes.is_empty() {
        anyhow::bail!("{r:?} selects no change to abandon");
    }
    println!(
        "{} {} selects {}:",
        ui::section("abandon"),
        ui::id(r),
        plural(hashes.len(), "change")
    );
    for h in &hashes {
        if let Some(m) = selected.metas.get(h) {
            println!(
                "  {} {}  {}",
                ui::id(m.change_id.short(8)),
                ui::hash(format!("#{}", h.short(12))),
                subject_of(&m.message)
            );
        }
    }
    const ASK_ABOVE: usize = 5;
    if hashes.len() > ASK_ABOVE && !yes {
        anyhow::bail!("that is more than {ASK_ABOVE} changes; pass --yes to abandon them all");
    }
    // Newest first: abandoning a change rewrites what depends on it, so a
    // later member is found again by its ChangeId.
    let mut done = 0;
    for h in &hashes {
        let Some(m) = selected.metas.get(h) else {
            continue;
        };
        let now = match repo.resolve_change(&m.change_id.to_hex()) {
            Ok(h) => h,
            Err(_) => continue,
        };
        abandon_one(&repo, now)?;
        done += 1;
    }
    println!("{} {}", ui::done("Abandoned"), plural(done, "change"));
    where_now(&repo);
    Ok(0)
}

fn abandon_one(repo: &Repo, h: ChangeHash) -> Result<()> {
    let c = repo.store().get_change_meta(&h)?;
    let notes = repo.abandon(&h)?;
    println!(
        "{} {} {}  {}",
        ui::done("Abandoned"),
        ui::id(c.change_id.short(8)),
        ui::hash(format!("#{}", h.short(12))),
        ui::dim("its content remains on disk as uncommitted work if the working copy sat on it")
    );
    for n in notes {
        println!("  {} {n}", ui::note());
    }
    Ok(())
}

pub fn checkpoint() -> Result<i32> {
    let repo = open()?;
    let sp = ui::spinner("Writing checkpoint…");
    let (r, changes, bytes) = repo.checkpoint()?;
    sp.done(&format!(
        "{} {} of {} ({} bytes) for {}",
        ui::done("Checkpoint"),
        ui::hash(format!("#{}", r.short(12))),
        plural(changes, "change"),
        bytes,
        ui::id(&repo.config.bookmark)
    ));
    Ok(0)
}

/// For shell prompts: silent (exit 1) outside a repository, otherwise one line.
pub fn prompt(format: &str, glyphs: bool, color: Option<&str>) -> Result<i32> {
    let Ok(repo) = Repo::open(&std::env::current_dir()?) else {
        return Ok(1);
    };
    let info = repo.quick_status()?;
    let fmt = if glyphs && format == oxy_core::repo::DEFAULT_PROMPT_FORMAT {
        oxy_core::repo::GLYPH_PROMPT_FORMAT
    } else {
        format
    };
    let line = match color {
        Some("bash") => info.format_colored(fmt, ("\\[", "\\]")),
        Some("zsh") => info.format_colored(fmt, ("%{", "%}")),
        Some(_) => info.format_colored(fmt, ("", "")),
        None => info.format(fmt),
    };
    println!("{line}");
    Ok(0)
}

pub fn sparse(paths: &[String]) -> Result<i32> {
    let mut repo = open()?;
    if paths.is_empty() {
        if repo.config.sparse_paths.is_empty() {
            println!("No sparse filter: the whole tree is materialized.");
        } else {
            println!("{}", ui::heading("Sparse filter"));
            for p in &repo.config.sparse_paths {
                println!("  {}", ui::path(p));
            }
        }
        return Ok(0);
    }
    let snap = repo.snapshot("oxy sparse")?;
    if !snap.wc.tree_ops.is_empty() || !snap.wc.edits.is_empty() {
        anyhow::bail!(
            "the working copy has changes; commit them before changing the sparse filter"
        );
    }
    repo.config.set("filter.paths", &paths.join(","))?;
    repo.save_config()?;
    let heads = repo.bookmark_heads()?;
    let sp = ui::spinner("Re-checking out with the new filter…");
    let r = repo.checkout(&heads, true, "oxy sparse (checkout)")?;
    sp.done(&format!(
        "{} {}: {} written, {} removed",
        ui::done("Sparse filter set to"),
        ui::path(paths.join(",")),
        plural(r.written, "file"),
        r.removed
    ));
    Ok(0)
}

pub fn tag_create(name: &str, changes: &[String], message: &str) -> Result<i32> {
    let repo = open()?;
    repo.snapshot_status("oxy tag")?;
    let heads = if changes.is_empty() {
        repo.bookmark_heads()?
    } else {
        let mut heads = Vec::new();
        for c in changes {
            heads.extend(repo.resolve_heads(c)?);
        }
        heads
    };
    let t = repo.tag_create(name, &heads, message)?;
    println!(
        "{} {} {} {} ({}){}",
        ui::done("Tagged"),
        ui::bookmark(&t.name),
        ui::dim(ui::glyph("→", "->")),
        ui::hash(format!("#{}", t.state.short(12))),
        plural(t.heads.len(), "head"),
        t.signer
            .map(|s| format!(", signed by {s}"))
            .unwrap_or_else(|| ui::dim(", unsigned"))
    );
    Ok(0)
}

pub fn tag_list(as_json: bool) -> Result<i32> {
    let repo = open()?;
    let tags = repo.tags()?;
    if as_json {
        println!(
            "{}",
            json::arr(tags.iter().map(|t| {
                json::obj([
                    ("name", json::s(&t.name)),
                    ("state", json::s(&t.state.to_hex())),
                    ("heads", json::hashes(&t.heads)),
                    ("message", json::s(&t.message)),
                    (
                        "signer",
                        json::opt(t.signer.as_ref(), |s| json::s(&s.to_string())),
                    ),
                ])
            }))
        );
        return Ok(0);
    }
    if tags.is_empty() {
        println!("{}", ui::dim("No tags."));
    }
    for t in tags {
        println!(
            "{} {} {}{}{}{}",
            ui::ok(ui::glyph("⚑", "#")),
            ui::bookmark(&t.name),
            // The heads, as `oxy log` shows changes, not the state hash.
            ui::hash(
                t.heads
                    .iter()
                    .map(|h| format!("#{}", h.short(12)))
                    .collect::<Vec<_>>()
                    .join(" ")
            ),
            ui::sep() + &ui::dim(plural(t.heads.len(), "head")),
            if t.message.is_empty() {
                String::new()
            } else {
                format!("  {}", ui::subject(subject_of(&t.message)))
            },
            t.signer
                .map(|s| ui::sep() + &ui::ok(format!("{} {s}", ui::glyph("✔", "v"))))
                .unwrap_or_default()
        );
    }
    Ok(0)
}

/// Whether `name` is a bookmark, here or only on a remote: what checkout
/// and workspace add take as "be on this bookmark" (oxygen#60).
fn names_bookmark(repo: &oxy_core::repo::Repo, name: &str) -> Result<bool> {
    Ok(repo.view()?.bookmarks.contains_key(name)
        || repo
            .remote_only_bookmarks()?
            .iter()
            .any(|b| b.name == name || format!("{}/{}", b.remote, b.name) == name))
}

pub fn workspace_add(path: &std::path::Path, changes: &[String]) -> Result<i32> {
    let repo = open()?;
    // One bookmark named: the new workspace is on it (oxygen#60), not on
    // this workspace's bookmark with that one's files.
    if let [name] = changes {
        if names_bookmark(&repo, name)? {
            let (local, _) = repo.local_bookmark_for(name)?;
            let heads = repo.resolve_heads(&local)?;
            let sp = ui::spinner(&format!("Creating workspace at {}…", path.display()));
            let ws = repo.workspace_add_on(path, Some(&heads), Some(&local))?;
            sp.done(&format!(
                "{} {} (workspace {}) on {}",
                ui::done("Workspace created at"),
                ui::path(ws.root().display()),
                ui::id(ws.workspace().short(8)),
                ui::bookmark(&local)
            ));
            return Ok(0);
        }
    }
    let heads = if changes.is_empty() {
        None
    } else {
        let mut heads = Vec::new();
        for c in changes {
            heads.extend(repo.resolve_heads(c)?);
        }
        Some(heads)
    };
    let sp = ui::spinner(&format!("Creating workspace at {}…", path.display()));
    let ws = repo.workspace_add(path, heads.as_deref())?;
    sp.done(&format!(
        "{} {} (workspace {})",
        ui::done("Workspace created at"),
        ui::path(ws.root().display()),
        ui::id(ws.workspace().short(8))
    ));
    Ok(0)
}

pub fn workspace_list(as_json: bool) -> Result<i32> {
    let repo = open()?;
    if as_json {
        println!(
            "{}",
            json::arr(repo.workspaces()?.iter().map(|w| {
                json::obj([
                    ("id", json::s(&w.id.to_hex())),
                    ("path", json::s(&w.path.to_string_lossy())),
                    ("current", json::b(w.current)),
                    (
                        "working_copy",
                        json::opt(w.working_copy, |h| json::s(&h.to_hex())),
                    ),
                ])
            }))
        );
        return Ok(0);
    }
    for w in repo.workspaces()? {
        println!(
            "{} {} {}{}",
            if w.current {
                ui::ok(ui::glyph("●", "*"))
            } else {
                ui::dim(ui::glyph("○", "o"))
            },
            ui::id(w.id.short(8)),
            ui::path(w.path.display()),
            w.working_copy
                .map(|h| ui::sep() + &ui::dim(format!("working copy #{}", h.short(12))))
                .unwrap_or_else(|| ui::sep() + &ui::warn("not in view"))
        );
    }
    Ok(0)
}

pub fn workspace_forget(spec: &str) -> Result<i32> {
    let repo = open()?;
    let all = repo.workspaces()?;
    let target = std::fs::canonicalize(spec).ok();
    let matches: Vec<_> = all
        .iter()
        .filter(|w| w.id.starts_with_hex(spec) || target.as_ref().is_some_and(|t| *t == w.path))
        .collect();
    let w = match matches.as_slice() {
        [w] => *w,
        [] => anyhow::bail!("no workspace matches {spec:?}"),
        _ => anyhow::bail!("{spec:?} is ambiguous"),
    };
    repo.workspace_forget(&w.id)?;
    println!(
        "{} workspace {} at {}; its files were left in place.",
        ui::done("Forgot"),
        ui::id(w.id.short(8)),
        ui::path(w.path.display())
    );
    Ok(0)
}

pub fn lock(path: &str) -> Result<i32> {
    let repo = open()?;
    repo.lock_path(path)?;
    println!(
        "{} {} {}",
        ui::done("Locked"),
        ui::path(path),
        ui::dim("(advisory, local)")
    );
    Ok(0)
}

pub fn unlock(path: &str) -> Result<i32> {
    let repo = open()?;
    repo.unlock_path(path)?;
    println!("{} {}", ui::done("Unlocked"), ui::path(path));
    Ok(0)
}

pub fn split(change: &str, paths: &[String]) -> Result<i32> {
    let repo = open()?;
    let h = repo.resolve_change(change)?;
    let (h1, h2) = repo.split(&h, paths)?;
    let c1 = repo.store().get_change_meta(&h1)?;
    let c2 = repo.store().get_change_meta(&h2)?;
    println!(
        "{} into {} {} and {} {}",
        ui::done("Split"),
        ui::id(c1.change_id.short(8)),
        ui::hash(format!("#{}", h1.short(12))),
        ui::id(c2.change_id.short(8)),
        ui::hash(format!("#{}", h2.short(12)))
    );
    Ok(0)
}

fn heads_from(repo: &Repo, changes: &[String]) -> Result<Vec<oxy_core::hash::ChangeHash>> {
    let mut heads = Vec::new();
    for c in changes {
        heads.extend(repo.resolve_heads(c)?);
    }
    Ok(heads)
}

pub fn bookmark_create(name: &str, changes: &[String], upto: bool, only: bool) -> Result<i32> {
    let repo = open()?;
    repo.snapshot_status("oxy bookmark create")?;
    let heads = if changes.is_empty() {
        None
    } else {
        let named = heads_from(&repo, changes)?;
        let (_, wc) = repo.working_copy()?;
        let gap = repo.state_gap(&wc.deps, &named)?;
        if upto {
            Some(gap.upto)
        } else if only || gap.earlier.is_empty() {
            Some(named)
        } else {
            anyhow::bail!(
                "{name} at {} would lack {} of the current state recorded before it:\n{}\n\
                 A state is its heads and what they depend on, not everything recorded before them.\n\
                 Pass --upto for everything of the current state up to {0} (as a Git branch would hold),\n\
                 or --only for just {0} and what it depends on.",
                changes.join(" "),
                plural(gap.earlier.len(), "change"),
                listed_changes(&repo, &gap.earlier)
            );
        }
    };
    let heads = repo.bookmark_create(name, heads.as_deref())?;
    println!(
        "{} bookmark {} {} {}",
        ui::done("Created"),
        ui::bookmark(name),
        ui::dim(ui::glyph("→", "->")),
        ui::dim(plural(heads.len(), "head"))
    );
    println!(
        "  {} {}",
        ui::note(),
        ui::dim(format!("switch to it with oxy bookmark switch {name}"))
    );
    Ok(0)
}

/// Up to five changes, newest last, as `  #hash subject` lines.
fn listed_changes(repo: &Repo, changes: &[oxy_core::hash::ChangeHash]) -> String {
    let shown = changes.len().min(5);
    let mut lines: Vec<String> = changes[changes.len() - shown..]
        .iter()
        .map(|h| {
            let subject = repo
                .store()
                .get_change(h)
                .map(|c| subject_of(&c.message).to_string())
                .unwrap_or_default();
            format!("  #{} {subject}", h.short(12))
        })
        .collect();
    if changes.len() > shown {
        lines.insert(0, format!("  … and {} earlier", changes.len() - shown));
    }
    lines.join("\n")
}

pub fn bookmark_set(name: &str, changes: &[String], upto: bool, only: bool) -> Result<i32> {
    let repo = open()?;
    repo.snapshot_status("oxy bookmark set")?;
    let named = heads_from(&repo, changes)?;
    // What the bookmark holds now and the new heads would leave out.
    let current = repo
        .bookmarks()?
        .into_iter()
        .find(|b| b.name == name)
        .map(|b| b.heads)
        .ok_or_else(|| anyhow::anyhow!("no bookmark {name}"))?;
    let gap = repo.state_gap(&current, &named)?;
    let heads = if upto {
        gap.upto
    } else if only || gap.earlier.is_empty() {
        named
    } else {
        anyhow::bail!(
            "{name} at {} would lose {} it holds now, recorded before it:\n{}\n\
             A state is its heads and what they depend on, not everything recorded before them.\n\
             Pass --upto to keep everything {name} holds up to {0} (as a Git branch would),\n\
             or --only for just {0} and what it depends on.",
            changes.join(" "),
            plural(gap.earlier.len(), "change"),
            listed_changes(&repo, &gap.earlier)
        );
    };
    let heads = repo.bookmark_set(name, &heads)?;
    println!(
        "{} bookmark {} {} {}",
        ui::done("Moved"),
        ui::bookmark(name),
        ui::dim(ui::glyph("→", "->")),
        ui::dim(plural(heads.len(), "head"))
    );
    Ok(0)
}

pub fn bookmark_delete(name: &str) -> Result<i32> {
    let repo = open()?;
    repo.bookmark_delete(name)?;
    println!(
        "{} bookmark {} {}",
        ui::done("Deleted"),
        ui::bookmark(name),
        ui::dim("(its changes stay until unreachable)")
    );
    Ok(0)
}

/// Heads with their metadata, newest first.
fn heads_newest_first(
    repo: &Repo,
    heads: &[oxy_core::hash::ChangeHash],
) -> Vec<(oxy_core::hash::ChangeHash, oxy_core::state::ChangeMeta)> {
    let mut out: Vec<_> = heads
        .iter()
        .filter_map(|h| repo.store().get_change_meta(h).ok().map(|m| (*h, m)))
        .collect();
    out.sort_by_key(|(_, m)| std::cmp::Reverse(m.hlc));
    out
}

/// One head as a line: id, hash, author, when, subject.
fn print_head(
    repo: &Repo,
    indent: &str,
    h: &oxy_core::hash::ChangeHash,
    m: &oxy_core::state::ChangeMeta,
) {
    println!(
        "{indent}{} {} {}{}{}{}{}",
        ui::id(m.change_id.short(8)),
        ui::dim(format!("#{}", &h.to_hex()[..8])),
        author_name(repo, m),
        ui::sep(),
        ui::dim(ui::ago(m.hlc.wall_ms)),
        ui::sep(),
        ui::subject(subject_of(&m.message))
    );
}

pub fn bookmark_show(name: Option<&str>, as_json: bool) -> Result<i32> {
    let repo = open()?;
    let name = name.unwrap_or(&repo.config.bookmark).to_string();
    let view = repo.view()?;
    let st = match view.bookmarks.get(&name) {
        Some(st) => *st,
        None => match oxy_core::repo::remote_bookmark(&view, &name) {
            Some((_, _, st)) => st,
            None => anyhow::bail!("no bookmark {name}: oxy bookmark list --all lists them"),
        },
    };
    let heads = repo.store().get_state(&st)?.heads;
    let shown = heads_newest_first(&repo, &heads);
    if as_json {
        println!(
            "{}",
            json::obj([
                ("name", json::s(&name)),
                ("current", json::b(name == repo.config.bookmark)),
                (
                    "heads",
                    json::arr(shown.iter().map(|(h, m)| {
                        json::obj([
                            ("hash", json::s(&h.to_hex())),
                            ("id", json::s(&m.change_id.to_string())),
                            ("author", json::s(&author_name(&repo, m))),
                            ("time_ms", json::n(m.hlc.wall_ms)),
                            ("subject", json::s(subject_of(&m.message))),
                        ])
                    }))
                ),
            ])
        );
        return Ok(0);
    }
    println!(
        "{} {}{}{}",
        ui::ok(ui::glyph("●", "*")),
        ui::bookmark(&name),
        ui::sep(),
        ui::dim(plural(heads.len(), "head"))
    );
    for (h, m) in &shown {
        print_head(&repo, "  ", h, m);
    }
    if heads.len() > 1 {
        println!(
            "  {}",
            ui::dim("None depends on another: the bookmark is all of them and their dependencies.")
        );
    }
    Ok(0)
}

pub fn bookmark_list(all: bool, verbose: bool, as_json: bool) -> Result<i32> {
    let repo = open()?;
    let remote_only = repo.remote_only_bookmarks()?;
    if as_json {
        let mut items: Vec<String> = repo
            .bookmarks()?
            .into_iter()
            .map(|b| {
                json::obj([
                    ("name", json::s(&b.name)),
                    ("heads", json::hashes(&b.heads)),
                    ("current", json::b(b.current)),
                    ("ahead", json::opt(b.ahead, json::n)),
                    ("behind", json::opt(b.behind, json::n)),
                    ("remote", json::opt(b.remote.as_deref(), json::s)),
                ])
            })
            .collect();
        if all {
            items.extend(remote_only.iter().map(|b| {
                json::obj([
                    ("name", json::s(&format!("{}/{}", b.remote, b.name))),
                    ("heads", json::hashes(&b.heads)),
                    ("current", json::b(false)),
                    ("ahead", "null".into()),
                    ("behind", "null".into()),
                    ("remote", json::s(&b.remote)),
                ])
            }));
        }
        println!("{}", json::arr(items));
        return Ok(0);
    }
    for b in repo.bookmarks()? {
        let mark = if b.current {
            ui::ok(ui::glyph("●", "*"))
        } else {
            ui::dim(ui::glyph("○", "o"))
        };
        let mut tail = String::new();
        if let Some(n) = b.ahead.filter(|n| *n > 0) {
            tail += &ui::ok(format!(" {}{n}", ui::glyph("↑", "+")));
        }
        if let Some(n) = b.behind.filter(|n| *n > 0) {
            tail += &ui::warn(format!(" {}{n}", ui::glyph("↓", "-")));
        }
        // Which remote, when there is a choice (oxygen#83).
        if !tail.is_empty() && repo.config.remotes.len() > 1 {
            if let Some(r) = &b.remote {
                tail += &ui::dim(format!(" {r}"));
            }
        }
        let shown = heads_newest_first(&repo, &b.heads);
        // The newest head's subject, so a busy bookmark shows its latest work.
        let head = match shown.first() {
            Some(_) if verbose => String::new(),
            Some((_, m)) if b.heads.len() > 1 => format!(
                "{} {}",
                ui::dim("newest"),
                ui::subject(subject_of(&m.message))
            ),
            Some((_, m)) => ui::subject(subject_of(&m.message)),
            None => ui::dim("(empty)"),
        };
        let head = if head.is_empty() {
            head
        } else {
            format!("  {head}")
        };
        println!(
            "{mark} {}{}{}{tail}{head}",
            ui::bookmark(&b.name),
            ui::sep(),
            ui::dim(plural(b.heads.len(), "head"))
        );
        if verbose {
            for (h, m) in &shown {
                print_head(&repo, "    ", h, m);
            }
        }
    }
    if remote_only.is_empty() {
        return Ok(0);
    }
    if !all {
        println!(
            "{}",
            ui::dim(format!(
                "  and {} only on a remote: oxy bookmark list --all",
                plural(remote_only.len(), "bookmark")
            ))
        );
        return Ok(0);
    }
    for b in &remote_only {
        println!(
            "{} {}{}{}",
            ui::dim(ui::glyph("◌", ".")),
            ui::dim(format!("{}/{}", b.remote, b.name)),
            ui::sep(),
            ui::dim(plural(b.heads.len(), "head"))
        );
    }
    println!(
        "  {} {}",
        ui::note(),
        ui::dim("oxy bookmark switch NAME makes a local bookmark from a remote's")
    );
    Ok(0)
}

pub fn bookmark_switch(name: &str, discard: bool, carry: bool) -> Result<i32> {
    let mut repo = open()?;
    let from = repo.config.bookmark.clone();
    let (local, created_from) = repo.local_bookmark_for(name)?;
    if let Some(remote) = created_from {
        println!(
            "{} {} from {}",
            ui::done("Created"),
            ui::bookmark(&local),
            ui::dim(format!("{remote}/{local}"))
        );
    }
    let name = local.as_str();
    // Only behind its remote: take the remote's state, so the switch does
    // not check out a stale one (oxygen#74).
    if let Some(n) = repo.catch_up_bookmark(name)? {
        println!(
            "{} {} with {}: {} it lacked",
            ui::done("Caught up"),
            ui::bookmark(name),
            ui::dim(format!("{}/{name}", repo.default_remote())),
            plural(n, "change")
        );
    }
    let sp = ui::spinner(&format!("Switching to {name}…"));
    let (r, carried) = if carry {
        repo.bookmark_switch_carry(name)?
    } else {
        (repo.bookmark_switch(name, discard)?, vec![])
    };
    sp.done(&format!(
        "{} to {}: {} written, {} removed{}",
        ui::done("Switched"),
        ui::bookmark(name),
        plural(r.written, "file"),
        r.removed,
        if carried.is_empty() {
            String::new()
        } else {
            format!("; carried {}", plural(carried.len(), "changed path"))
        }
    ));
    print_removed(&r);
    print_carried(&carried);
    print_kept_both(&r);
    if r.conflicted {
        println!(
            "  {} {}",
            ui::caution(),
            ui::warn("this state has conflicts; see oxy status")
        );
    }
    // Say when the new state leaves out work the old one had: a state is
    // its heads and what they depend on, which can be far less than a Git
    // user expects.
    if r.lacks > 0 {
        println!(
            "  {} {}",
            ui::note(),
            ui::dim(format!(
                "{name} lacks {} that {from} has",
                plural(r.lacks, "change")
            ))
        );
    }
    super::sync::subrepos_behind(&repo);
    where_now(&repo);
    Ok(0)
}

pub fn merge(bookmark: &str) -> Result<i32> {
    let repo = open()?;
    let sp = ui::spinner(&format!("Merging {bookmark}…"));
    let r = repo.merge(bookmark)?;
    if !r.changed {
        sp.done(&format!(
            "{} {}",
            ui::ok(ui::glyph("✔", "*")),
            ui::dim(format!(
                "{} already contains {bookmark}",
                repo.config.bookmark
            ))
        ));
        return Ok(0);
    }
    sp.done(&format!(
        "{} {} into {}: now {}{}",
        ui::done("Merged"),
        ui::bookmark(bookmark),
        ui::bookmark(&repo.config.bookmark),
        plural(r.heads.len(), "head"),
        ui::dim(if r.checked_out {
            "; working copy updated"
        } else {
            "; run oxy checkout to update the working copy"
        })
    ));
    let snap = repo.snapshot("oxy merge")?;
    if snap.base_snapshot.is_conflicted() {
        println!(
            "  {} {}",
            ui::caution(),
            ui::warn("the result has conflicts; see oxy status")
        );
    }
    where_now(&repo);
    Ok(0)
}

pub fn squash(change: &str, into: &str) -> Result<i32> {
    let repo = open()?;
    let c = repo.resolve_change(change)?;
    let d = repo.resolve_change(into)?;
    let sp = ui::spinner("Squashing…");
    let h = repo.squash(&c, &d)?;
    let new = repo.store().get_change_meta(&h)?;
    sp.done(&format!(
        "{} into {} {}  {}",
        ui::done("Squashed"),
        ui::id(new.change_id.short(8)),
        ui::hash(format!("#{}", h.short(12))),
        ui::subject(subject_of(&new.message))
    ));
    Ok(0)
}

pub fn rebase(change: &str, onto: &[String], into_working_copy: bool) -> Result<i32> {
    let repo = open()?;
    let c = repo.resolve_change(change)?;
    let mut heads = Vec::new();
    for o in onto {
        heads.extend(repo.resolve_heads(o)?);
    }
    let sp = ui::spinner("Rebasing…");
    let h = match repo.rebase(&c, &heads) {
        Err(oxy_core::repo::RepoError::Conflicted(_)) if into_working_copy => {
            let r = repo.rebase_into_working_copy(&c, &heads)?;
            sp.done(&format!(
                "{} {} into {}: now {}",
                ui::done("Merged"),
                onto.join(" "),
                ui::bookmark(&repo.config.bookmark),
                plural(r.heads.len(), "head"),
            ));
            if r.checked_out {
                println!(
                    "  {} {}",
                    ui::caution(),
                    ui::warn("the conflict is in the working copy: fix the marked files (see oxy status), then oxy commit")
                );
            } else {
                println!(
                    "  {} {}",
                    ui::caution(),
                    ui::warn("the working copy has changes of its own: commit or discard them, then oxy checkout to take the conflict in")
                );
            }
            where_now(&repo);
            return Ok(0);
        }
        other => other?,
    };
    let new = repo.store().get_change_meta(&h)?;
    sp.done(&format!(
        "{} {} {}  {}",
        ui::done("Rebased"),
        ui::id(new.change_id.short(8)),
        ui::hash(format!("#{}", h.short(12))),
        ui::dim(format!(
            "now depends on {}",
            plural(new.deps.len(), "change")
        ))
    ));
    where_now(&repo);
    Ok(0)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn id_prefixes_agree_with_the_whole_list() {
        // Ids that share long prefixes, and some that differ only in a
        // half byte, from a fixed sequence.
        let mut x: u64 = 0x9e37_79b9_7f4a_7c15;
        let mut next = || {
            x ^= x << 13;
            x ^= x >> 7;
            x ^= x << 17;
            x
        };
        let mut ids: Vec<[u8; 16]> = Vec::new();
        for _ in 0..2000 {
            let mut id = [0u8; 16];
            id[..8].copy_from_slice(&next().to_le_bytes());
            id[8..].copy_from_slice(&next().to_le_bytes());
            let share = (next() % 4) as usize;
            if let Some(prev) = ids.last() {
                id[..share].copy_from_slice(&prev[..share]);
                if next() % 2 == 0 {
                    id[share] = (prev[share] & 0xf0) | (id[share] & 0x0f);
                }
            }
            ids.push(id);
        }
        let hex = |id: &[u8; 16]| oxy_core::ids::ChangeId(*id).to_hex();
        let whole = unique_prefixes(ids.iter().map(hex));
        let some = id_prefixes(ids.clone(), ids.iter().copied());
        for id in &ids {
            assert_eq!(some[id], whole[&hex(id)], "{}", hex(id));
        }
    }
}
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