History-only states: log, log of a path and blame_in load changes and tree only, deferring file edits; load_graphs builds the graphs a command needs from checkpoint blobs or by replay, identical to a full load; an unloaded graph is never read as empty e8d38e47e9d7

closes #10

Author: Andy McCall @andymccall <[email protected]>
When: 1 month ago · 2026-09-28 20:20 UTC
Signature: ✔ signed by Andy McCall
Hash: e8d38e47e9d796a9ead60d554c5e6eb223acaa1eec5922e59bfbecaa5fa939a0
Depends on: 0bdc3f91a39f 119bbf50cb86 20247a03a596 252e8cb23fbc 75167672ebcd 957fee30826e 982864068a59 afaba5f1306d bc489b6c7f69 e02bf0cd0533 e7ddd552b619 ff0af1ee299d
Depended on by: c2e1d09047db 5552e69c7325 d45dab0484ea 36e51aa806c6 3f1b8fe25ec9 f9575918477f dbf06d342e1d e83354cdac22 f6451fbbae3f 4d6c9c1b358c 57d8dc05c9d4 519c7c061bcb 01a47cd7f0c8 69816d688300 a4fad5b085c7 86e1824f2d0b dfb23a3a8cfa cc7a00565161
In bookmarks: agents-in-readme bare-hashes carried-not-removed carry-identical doctor-trust identical-sides keyless-tags main merge-remote-bookmark only-help-103 paths-for-resolutions-and-amend push-notes show-stat subrepo-pin-state switch-says
In tags: v0.1.0 v0.10.0 v0.11.0 v0.2.0 v0.3.0 v0.3.1 v0.4.0 v0.4.1 v0.4.2 v0.4.3 v0.4.4 v0.4.5 v0.4.6 v0.5.0 v0.5.1 v0.6.0 v0.7.0 v0.8.0 v0.9.0
Edits: 29 atoms, 0 tree operations, 5 files

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modified crates/oxy-core/src/repo/checkpoint.rs +14 −1

modified crates/oxy-core/src/repo/inspect.rs +7 −2

modified crates/oxy-core/src/repo/mod.rs +27 −3

modified crates/oxy-core/src/repo/snapshot.rs +1 −1

modified crates/oxy-core/src/state.rs +393 −6

		…	155 unchanged lines
156	156
157	157		/// Load the state of `heads` using a checkpoint when one applies.
158	158		pub(crate) fn load_state_checkpointed(&self, heads: &[ChangeHash]) -> Result<Option<State>> {
	159	+	self.load_state_checkpointed_as(heads, false)
	160	+	}
	161	+
	162	+	/// As [`Repo::load_state_checkpointed`]; `history` builds no file graph.
	163	+	pub(crate) fn load_state_checkpointed_as(
	164	+	&self,
	165	+	heads: &[ChangeHash],
	166	+	history: bool,
	167	+	) -> Result<Option<State>> {
159	168		let mut bookmarks: Vec<String> = vec![self.config.bookmark.clone()];
160	169		if let Ok(rd) = fs::read_dir(self.oxy.join("checkpoints")) {
161	170		for e in rd.flatten() {
		…	13 unchanged lines
175	184		};
176	185		let base = {
177	186		let _t = crate::timing::phase("load: decode checkpoint");
178		-	self.state_from_checkpoint(&payload)?
	187	+	if history {
	188	+	State::from_checkpoint_history(&payload)?
	189	+	} else {
	190	+	self.state_from_checkpoint(&payload)?
	191	+	}
179	192		};
180	193		let cp_heads: BTreeSet<ChangeHash> = cp.heads.iter().copied().collect();
181	194		let mut found: BTreeSet<ChangeHash> = BTreeSet::new();
		…	31 unchanged lines

		…	69 unchanged lines
70	70
71	71		/// Blame `path` in the state with these heads (hosted repositories).
72	72		pub fn blame_in(&self, path: &str, heads: &[ChangeHash]) -> Result<Vec<BlameLine>> {
73		-	let state = self.load_state(heads)?;
74		-	self.blame_of(&state, &state.tree().view(), path)
	73	+	// Only the one file's graph is built.
	74	+	let mut state = self.load_state_history(heads)?;
	75	+	let tree = state.tree().view();
	76	+	if let Some(e) = tree.entries.get(path) {
	77	+	self.load_graphs_of(&mut state, &[e.node])?;
	78	+	}
	79	+	self.blame_of(&state, &tree, path)
75	80		}
76	81
77	82		/// Blame `path` in a loaded state whose tree view the caller holds; no
		…	294 unchanged lines

		…	777 unchanged lines
778	778		self.load_state_full(heads)
779	779		}
780	780
	781	+	/// The state of `heads` for its history (changes, tree, metadata) with
	782	+	/// no file graph built: much cheaper than [`Repo::load_state`] for log
	783	+	/// and friends. Build the graphs a command needs with
	784	+	/// [`Repo::load_graphs_of`].
	785	+	pub fn load_state_history(&self, heads: &[ChangeHash]) -> Result<State> {
	786	+	if let Some(st) = self.load_state_checkpointed_as(heads, true)? {
	787	+	return Ok(st);
	788	+	}
	789	+	self.load_state_replayed(heads, State::new_history_only())
	790	+	}
	791	+
	792	+	/// Build these file graphs in a history-only state.
	793	+	pub fn load_graphs_of(&self, state: &mut State, nodes: &[crate::ids::NodeId]) -> Result<()> {
	794	+	Ok(state.load_graphs(nodes, \|refs\| {
	795	+	self.read_blobs(refs).map_err(\|e\| {
	796	+	crate::objects::ObjectError::Schema(format!("checkpoint graph blobs: {e}"))
	797	+	})
	798	+	})?)
	799	+	}
	800	+
781	801		/// Load the dependency closure of `heads` change by change.
782	802		pub fn load_state_full(&self, heads: &[ChangeHash]) -> Result<State> {
783		-	let mut state = State::new();
	803	+	self.load_state_replayed(heads, State::new())
	804	+	}
	805	+
	806	+	fn load_state_replayed(&self, heads: &[ChangeHash], mut state: State) -> Result<State> {
784	807		let mut stack: Vec<ChangeHash> = heads.to_vec();
785	808		let mut seen: BTreeSet<ChangeHash> = BTreeSet::new();
786	809		{
		…	486 unchanged lines
1273	1296		let (wc_hash, _) = self.working_copy()?;
1274	1297		let mut all = heads.clone();
1275	1298		all.push(wc_hash);
1276		-	let state = self.load_state(&all)?;
	1299	+	let state = self.load_state_history(&all)?;
1277	1300		let head_set: BTreeSet<ChangeHash> = heads.into_iter().collect();
1278	1301		let mut entries: Vec<LogEntry> = Vec::new();
1279	1302		for (h, meta) in state.changes() {
		…	29 unchanged lines
1309	1332		/// The log of the state with these heads, newest first, with no working
1310	1333		/// copy involved (for hosted repositories and any explicit state).
1311	1334		pub fn log_state(&self, heads: &[ChangeHash]) -> Result<Vec<LogEntry>> {
1312		-	Ok(self.log_of(&self.load_state(heads)?))
	1335	+	// The log needs change metadata only: no file graph is built.
	1336	+	Ok(self.log_of(&self.load_state_history(heads)?))
1313	1337		}
1314	1338
1315	1339		/// The log of a state already loaded, newest first.
		…	187 unchanged lines

		…	1138 unchanged lines
1139	1139		/// The log of the state with these heads restricted to changes touching
1140	1140		/// `path` (its node, so renames are followed).
1141	1141		pub fn log_for_path_in(&self, path: &str, heads: &[ChangeHash]) -> Result<Vec<LogEntry>> {
1142		-	self.log_for_path_of(&self.load_state(heads)?, path, None)
	1142	+	self.log_for_path_of(&self.load_state_history(heads)?, path, None)
1143	1143		}
1144	1144
1145	1145		/// The changes of a loaded state touching `path`, newest first, at most
		…	944 unchanged lines

`/`	Search
`g` `c`	Code
`g` `h`	History
`g` `b`	Bookmarks
`g` `t`	Trust
`y`	Permalink to this state (files and trees)
`?`	This sheet

		…	61 unchanged lines
62	62		/// Memoised transitive dependencies. A mutex, not a `RefCell`, so a
63	63		/// loaded state can be shared across threads by a host that caches it.
64	64		closure: Mutex<HashMap<ChangeHash, Arc<HashSet<ChangeHash>>>>,
	65	+	/// `None` for a full state. For a history-only state (loaded for its
	66	+	/// changes and tree), the file graphs not built yet, by node: `files`
	67	+	/// holds only those loaded with [`State::load_graphs`].
	68	+	deferred: Option<HashMap<NodeId, Deferred>>,
65	69		}
66	70
	71	+	/// A file graph a history-only state has not built: its base from a
	72	+	/// version 2 checkpoint, if any, and the edits of later changes in the
	73	+	/// order they were applied (spec §11). Building it later gives the same
	74	+	/// graph, since graph construction does not depend on order (§8).
	75	+	#[derive(Clone, Default)]
	76	+	struct Deferred {
	77	+	base: Option<DeferredBase>,
	78	+	edits: Vec<(ChangeHash, Vec<Edit>)>,
	79	+	}
	80	+
	81	+	#[derive(Clone)]
	82	+	enum DeferredBase {
	83	+	Inline(Value),
	84	+	Blob(ObjectRef),
	85	+	}
	86	+
67	87		impl Clone for State {
68	88		fn clone(&self) -> State {
69	89		State {
		…	2 unchanged lines
72	92		files: self.files.clone(),
73	93		replaces: self.replaces.clone(),
74	94		closure: Mutex::new(self.closure.lock().unwrap().clone()),
	95	+	deferred: self.deferred.clone(),
75	96		}
76	97		}
77	98		}
		…	82 unchanged lines
160	181		mode: *mode,
161	182		},
162	183		add @ TreeOp::AddNode { .. } => add.clone(),
	184	+	}
	185	+	}
	186	+
	187	+	/// Apply one change's edits of one file (inserts and deletes; replaces
	188	+	/// live beside the graphs) to that file's graph.
	189	+	fn apply_file_edits(g: &mut FileGraph, h: ChangeHash, edits: Vec<Edit>) {
	190	+	let mut next = 0u32;
	191	+	for e in edits {
	192	+	match e {
	193	+	Edit::Insert {
	194	+	after,
	195	+	before,
	196	+	lines,
	197	+	..
	198	+	} => {
	199	+	let first = next;
	200	+	next += lines.len() as u32;
	201	+	g.insert_owned(
	202	+	h,
	203	+	first,
	204	+	vertex(after.resolve(h)),
	205	+	vertex(before.resolve(h)),
	206	+	lines,
	207	+	);
	208	+	}
	209	+	Edit::Delete { atoms, .. } => {
	210	+	for r in atoms {
	211	+	g.delete(h, &r.resolve(h));
	212	+	}
	213	+	}
	214	+	Edit::Replace { .. } => {}
	215	+	}
163	216		}
164	217		}
165	218
166	219		impl State {
167	220		pub fn new() -> Self {
168	221		Self::default()
	222	+	}
	223	+
	224	+	/// An empty state for history only: changes and tree are kept, file
	225	+	/// edits are recorded but no file graph is built until
	226	+	/// [`State::load_graphs`] asks for it. For log and other commands that
	227	+	/// need no file contents, or only a few files.
	228	+	pub fn new_history_only() -> Self {
	229	+	State {
	230	+	deferred: Some(HashMap::new()),
	231	+	..Self::default()
	232	+	}
	233	+	}
	234	+
	235	+	/// Whether this state holds every file graph.
	236	+	pub fn is_full(&self) -> bool {
	237	+	self.deferred.as_ref().is_none_or(\|d\| d.is_empty())
	238	+	}
	239	+
	240	+	/// The graph of `node`, which must be loaded: asking a history-only
	241	+	/// state for a graph it has not built is a bug, never an empty file.
	242	+	fn graph(&self, node: &NodeId) -> Option<&FileGraph> {
	243	+	if let Some(d) = &self.deferred {
	244	+	assert!(
	245	+	!d.contains_key(node),
	246	+	"file graph {} of a history-only state was not loaded (State::load_graphs)",
	247	+	node.short(12)
	248	+	);
	249	+	}
	250	+	self.files.get(node)
	251	+	}
	252	+
	253	+	/// Operations over every file need every graph.
	254	+	fn require_full(&self, what: &str) {
	255	+	assert!(
	256	+	self.is_full(),
	257	+	"{what} needs every file graph; this state was loaded for history only"
	258	+	);
	259	+	}
	260	+
	261	+	/// Build the graphs of `nodes` in a history-only state: from their
	262	+	/// checkpoint base (blobs read in one batch through `load`) and their
	263	+	/// deferred edits. Nodes already built, or with no graph, are skipped.
	264	+	pub fn load_graphs(
	265	+	&mut self,
	266	+	nodes: &[NodeId],
	267	+	load: impl FnOnce(&[ObjectRef]) -> Result<Vec<Vec<u8>>, ObjectError>,
	268	+	) -> Result<(), ObjectError> {
	269	+	let Some(deferred) = self.deferred.as_mut() else {
	270	+	return Ok(());
	271	+	};
	272	+	let mut taken: Vec<(NodeId, Deferred)> = nodes
	273	+	.iter()
	274	+	.filter_map(\|n\| deferred.remove(n).map(\|d\| (*n, d)))
	275	+	.collect();
	276	+	let refs: Vec<ObjectRef> = taken
	277	+	.iter()
	278	+	.filter_map(\|(_, d)\| match &d.base {
	279	+	Some(DeferredBase::Blob(r)) => Some(*r),
	280	+	_ => None,
	281	+	})
	282	+	.collect();
	283	+	let mut blobs = if refs.is_empty() {
	284	+	Vec::new()
	285	+	} else {
	286	+	load(&refs)?
	287	+	}
	288	+	.into_iter();
	289	+	for (node, d) in taken.iter_mut() {
	290	+	let mut graph = match d.base.take() {
	291	+	Some(DeferredBase::Inline(v)) => FileGraph::from_value(&v)?,
	292	+	Some(DeferredBase::Blob(_)) => {
	293	+	let bytes = blobs
	294	+	.next()
	295	+	.ok_or_else(\|\| ObjectError::Schema("graph blobs: wrong count".into()))?;
	296	+	FileGraph::from_value(&cbor::decode(&bytes)?)?
	297	+	}
	298	+	None => FileGraph::default(),
	299	+	};
	300	+	for (h, edits) in std::mem::take(&mut d.edits) {
	301	+	apply_file_edits(&mut graph, h, edits);
	302	+	}
	303	+	self.files.insert(*node, graph);
	304	+	}
	305	+	Ok(())
169	306		}
170	307
171	308		pub fn len(&self) -> usize {
		…	15 unchanged lines
187	324		&self.tree
188	325		}
189	326		pub fn file(&self, node: &NodeId) -> Option<&FileGraph> {
190		-	self.files.get(node)
	327	+	self.graph(node)
191	328		}
192	329
193	330		/// Add a change whose dependencies are already present.
		…	28 unchanged lines
222	359		/// Serialize the whole state in payload version 1: change metadata,
223	360		/// tree, file graphs, replaces, all in one value (spec §11).
224	361		pub fn checkpoint_payload(&self) -> Vec<u8> {
	362	+	self.require_full("a checkpoint");
225	363		let mut nodes: Vec<&NodeId> = self.files.keys().collect();
226	364		nodes.sort();
227	365		let files = Value::Array(
		…	9 unchanged lines
237	375		/// (spec §11): the graphs of large files become blobs of their own.
238	376		pub fn checkpoint_file_graphs(&self) -> Vec<(NodeId, Vec<u8>)> {
239	377		use rayon::prelude::*;
	378	+	self.require_full("a checkpoint");
240	379		let mut nodes: Vec<(&NodeId, &FileGraph)> = self.files.iter().collect();
241	380		nodes.sort_by_key(\|(n, _)\| **n);
242	381		nodes
		…	168 unchanged lines
411	550		}
412	551		}
413	552		Ok(out)
	553	+	}
	554	+
	555	+	/// Decode a checkpoint payload for history only: a version 2 payload's
	556	+	/// graphs are noted, not read or built, and come later through
	557	+	/// [`State::load_graphs`]. A version 1 payload holds them inline and is
	558	+	/// decoded in full.
	559	+	pub fn from_checkpoint_history(bytes: &[u8]) -> Result<State, ObjectError> {
	560	+	let v = cbor::decode(bytes)?;
	561	+	let m = o::map(&v, "checkpoint payload")?;
	562	+	let version = o::uint(o::field(m, 0, "version")?, "version")?;
	563	+	if version != CHECKPOINT_INDEX_VERSION {
	564	+	return State::from_checkpoint_payload(bytes);
	565	+	}
	566	+	let mut st = State::payload_common(m)?;
	567	+	let mut deferred = HashMap::new();
	568	+	for f in o::array(o::field(m, 3, "files")?, "files")? {
	569	+	let e = o::array(f, "file")?;
	570	+	if e.len() != 2 {
	571	+	return Err(ObjectError::Schema("file: expected [node, graph]".into()));
	572	+	}
	573	+	let node = NodeId::from_slice(o::bytes(&e[0], "node")?)
	574	+	.ok_or_else(\|\| ObjectError::Schema("node: expected 16 bytes".into()))?;
	575	+	let base = match &e[1] {
	576	+	Value::Bytes(_) => DeferredBase::Blob(o::oref(&e[1], "graph blob")?),
	577	+	other => DeferredBase::Inline(other.clone()),
	578	+	};
	579	+	deferred.insert(
	580	+	node,
	581	+	Deferred {
	582	+	base: Some(base),
	583	+	edits: Vec::new(),
	584	+	},
	585	+	);
	586	+	}
	587	+	st.deferred = Some(deferred);
	588	+	Ok(st)
414	589		}
415	590
416	591		/// Changes, tree and replaces of a payload of either version.
		…	67 unchanged lines
484	659		for (i, op) in c.tree_ops.iter().enumerate() {
485	660		self.tree.apply(h, i as u32, &resolve_tree_op(op, h));
486	661		}
	662	+	if let Some(deferred) = self.deferred.as_mut() {
	663	+	// History only: edits of files not built wait, grouped per file.
	664	+	let mut per_node: HashMap<NodeId, Vec<Edit>> = HashMap::new();
	665	+	for e in c.edits {
	666	+	match e {
	667	+	Edit::Replace { node, old, new } => {
	668	+	self.replaces.entry(node).or_default().push((h, old, new))
	669	+	}
	670	+	e => per_node.entry(e.node()).or_default().push(e),
	671	+	}
	672	+	}
	673	+	for (node, edits) in per_node {
	674	+	match self.files.get_mut(&node) {
	675	+	Some(g) => apply_file_edits(g, h, edits),
	676	+	None => deferred.entry(node).or_default().edits.push((h, edits)),
	677	+	}
	678	+	}
	679	+	return;
	680	+	}
487	681		let mut counters: HashMap<NodeId, u32> = HashMap::new();
488	682		for e in c.edits {
489	683		match e {
		…	88 unchanged lines
578	772		}
579	773
580	774		pub fn materialize_file(&self, node: &NodeId) -> Materialized {
581		-	self.files
582		-	.get(node)
	775	+	self.graph(node)
583	776		.map(\|g\| g.materialize(self))
584	777		.unwrap_or_default()
585	778		}
586	779
587	780		/// Live lines of a text node in materialized order.
588	781		pub fn live_lines(&self, node: &NodeId) -> Vec<(AtomKey, Vec<u8>)> {
589		-	let Some(g) = self.files.get(node) else {
	782	+	let Some(g) = self.graph(node) else {
590	783		return vec![];
591	784		};
592	785		let m = g.materialize(self);
		…	74 unchanged lines
667	860
668	861		pub fn conflict_regions(&self, node: &NodeId) -> ConflictRegions {
669	862		let mut out = ConflictRegions::default();
670		-	let Some(g) = self.files.get(node) else {
	863	+	let Some(g) = self.graph(node) else {
671	864		return out;
672	865		};
673	866		let m = g.materialize(self);
		…	31 unchanged lines
705	898		}
706	899
707	900		pub fn render_file(&self, node: &NodeId) -> (Vec<u8>, Materialized) {
708		-	let Some(g) = self.files.get(node) else {
	901	+	let Some(g) = self.graph(node) else {
709	902		return (Vec::new(), Materialized::default());
710	903		};
711	904		let m = g.materialize(self);
		…	5 unchanged lines
717	910		/// rendering them is most of a snapshot's cost in a large tree.
718	911		pub fn materialize(&self) -> Snapshot {
719	912		use rayon::prelude::*;
	913	+	self.require_full("materializing a state");
720	914		let tree = self.tree.view();
721	915		let entries: Vec<(&String, &crate::tree::TreeEntry)> = tree.entries.iter().collect();
722	916		let rendered: Vec<(String, FileState)> = entries
		…	309 unchanged lines
1032	1226		matches!(&b.files["a"].content, FileContent::Text { bytes, .. } if bytes == b"2\n3\n")
1033	1227		);
1034	1228		assert!(State::from_checkpoint_payload(b"nonsense").is_err());
	1229	+	}
	1230	+
	1231	+	/// History-only states (O10f): the same state as a full load once its
	1232	+	/// graphs are built, by replay and from a version 2 checkpoint with
	1233	+	/// later changes; unloaded graphs are never read as empty.
	1234	+	#[test]
	1235	+	fn history_only_states_build_the_same_graphs_on_demand() {
	1236	+	let small = NodeId::random();
	1237	+	let big = NodeId::random();
	1238	+	let add = \|node: NodeId, name: &str\| TreeOp::AddNode {
	1239	+	node,
	1240	+	kind: NodeKind::File,
	1241	+	mode: Mode::TEXT,
	1242	+	parent: NodeId::ROOT,
	1243	+	name: name.into(),
	1244	+	};
	1245	+	let lines: Vec<Vec<u8>> = (0..300)
	1246	+	.map(\|i\| format!("line {i}\n").into_bytes())
	1247	+	.collect();
	1248	+	let c1 = change(
	1249	+	vec![],
	1250	+	vec![add(small, "small"), add(big, "big")],
	1251	+	vec![
	1252	+	Edit::Insert {
	1253	+	node: small,
	1254	+	after: AtomRef::Start,
	1255	+	before: AtomRef::End,
	1256	+	lines: vec![b"x\n".to_vec()],
	1257	+	},
	1258	+	Edit::Insert {
	1259	+	node: big,
	1260	+	after: AtomRef::Start,
	1261	+	before: AtomRef::End,
	1262	+	lines,
	1263	+	},
	1264	+	],
	1265	+	);
	1266	+	let h1 = c1.hash();
	1267	+	let c2 = change(
	1268	+	vec![h1],
	1269	+	vec![],
	1270	+	vec![
	1271	+	Edit::Delete {
	1272	+	node: big,
	1273	+	atoms: vec![AtomRange {
	1274	+	change: h1,
	1275	+	from: 2,
	1276	+	to: 9,
	1277	+	}],
	1278	+	},
	1279	+	Edit::Insert {
	1280	+	node: big,
	1281	+	after: AtomRef::Atom {
	1282	+	change: h1,
	1283	+	index: 20,
	1284	+	},
	1285	+	before: AtomRef::Atom {
	1286	+	change: h1,
	1287	+	index: 21,
	1288	+	},
	1289	+	lines: vec![b"new a\n".to_vec(), b"new b\n".to_vec()],
	1290	+	},
	1291	+	Edit::Insert {
	1292	+	node: small,
	1293	+	after: AtomRef::Atom {
	1294	+	change: h1,
	1295	+	index: 0,
	1296	+	},
	1297	+	before: AtomRef::End,
	1298	+	lines: vec![b"y\n".to_vec()],
	1299	+	},
	1300	+	],
	1301	+	);
	1302	+	let h2 = c2.hash();
	1303	+	let c3 = change(
	1304	+	vec![h2],
	1305	+	vec![],
	1306	+	vec![Edit::Delete {
	1307	+	node: small,
	1308	+	atoms: vec![AtomRange {
	1309	+	change: h1,
	1310	+	from: 0,
	1311	+	to: 1,
	1312	+	}],
	1313	+	}],
	1314	+	);
	1315	+
	1316	+	let mut full = State::new();
	1317	+	for c in [&c1, &c2, &c3] {
	1318	+	full.add(c.clone()).unwrap();
	1319	+	}
	1320	+	// By replay: nothing built until asked, then exactly the full graphs.
	1321	+	let mut hist = State::new_history_only();
	1322	+	for c in [&c1, &c2, &c3] {
	1323	+	hist.add(c.clone()).unwrap();
	1324	+	}
	1325	+	assert!(!hist.is_full() && hist.files.is_empty(), "no graph built");
	1326	+	assert_eq!(hist.len(), 3);
	1327	+	hist.load_graphs(&[big], \|_\| unreachable!("no checkpoint"))
	1328	+	.unwrap();
	1329	+	assert_eq!(
	1330	+	hist.render_file(&big).0,
	1331	+	full.render_file(&big).0,
	1332	+	"one file on its own"
	1333	+	);
	1334	+	assert!(!hist.is_full());
	1335	+	hist.load_graphs(&[small, big], \|_\| unreachable!()).unwrap();
	1336	+	assert!(hist.is_full());
	1337	+	assert_eq!(hist.checkpoint_payload(), full.checkpoint_payload());
	1338	+
	1339	+	// From a version 2 checkpoint of c1+c2, then c3 applied later.
	1340	+	let mut base = State::new();
	1341	+	base.add(c1.clone()).unwrap();
	1342	+	base.add(c2.clone()).unwrap();
	1343	+	let graphs = base.checkpoint_file_graphs();
	1344	+	let mut blobs: HashMap<ObjectRef, Vec<u8>> = HashMap::new();
	1345	+	let index = base.checkpoint_index(&graphs, \|enc\| {
	1346	+	let r = crate::hash::hash_object(crate::hash::ObjectType::Blob, enc);
	1347	+	blobs.insert(r, enc.to_vec());
	1348	+	r
	1349	+	});
	1350	+	let mut from_cp = State::from_checkpoint_history(&index).unwrap();
	1351	+	from_cp.add(c3.clone()).unwrap();
	1352	+	assert!(!from_cp.is_full());
	1353	+	let mut fetched = 0;
	1354	+	from_cp
	1355	+	.load_graphs(&[small, big], \|refs\| {
	1356	+	fetched += refs.len();
	1357	+	refs.iter()
	1358	+	.map(\|r\| {
	1359	+	blobs
	1360	+	.get(r)
	1361	+	.cloned()
	1362	+	.ok_or_else(\|\| ObjectError::Schema("missing".into()))
	1363	+	})
	1364	+	.collect()
	1365	+	})
	1366	+	.unwrap();
	1367	+	assert_eq!(
	1368	+	fetched, 1,
	1369	+	"the large graph's blob, in one batch; the small one was inline"
	1370	+	);
	1371	+	assert_eq!(from_cp.checkpoint_payload(), full.checkpoint_payload());
	1372	+	}
	1373	+
	1374	+	#[test]
	1375	+	#[should_panic(expected = "was not loaded")]
	1376	+	fn a_history_only_state_never_reads_an_unloaded_graph_as_empty() {
	1377	+	let f = NodeId::random();
	1378	+	let mut st = State::new_history_only();
	1379	+	st.add(change(
	1380	+	vec![],
	1381	+	vec![TreeOp::AddNode {
	1382	+	node: f,
	1383	+	kind: NodeKind::File,
	1384	+	mode: Mode::TEXT,
	1385	+	parent: NodeId::ROOT,
	1386	+	name: "a".into(),
	1387	+	}],
	1388	+	vec![Edit::Insert {
	1389	+	node: f,
	1390	+	after: AtomRef::Start,
	1391	+	before: AtomRef::End,
	1392	+	lines: vec![b"a\n".to_vec()],
	1393	+	}],
	1394	+	))
	1395	+	.unwrap();
	1396	+	st.render_file(&f);
	1397	+	}
	1398	+
	1399	+	#[test]
	1400	+	#[should_panic(expected = "needs every file graph")]
	1401	+	fn materializing_a_history_only_state_is_refused() {
	1402	+	let f = NodeId::random();
	1403	+	let mut st = State::new_history_only();
	1404	+	st.add(change(
	1405	+	vec![],
	1406	+	vec![TreeOp::AddNode {
	1407	+	node: f,
	1408	+	kind: NodeKind::File,
	1409	+	mode: Mode::TEXT,
	1410	+	parent: NodeId::ROOT,
	1411	+	name: "a".into(),
	1412	+	}],
	1413	+	vec![Edit::Insert {
	1414	+	node: f,
	1415	+	after: AtomRef::Start,
	1416	+	before: AtomRef::End,
	1417	+	lines: vec![b"a\n".to_vec()],
	1418	+	}],
	1419	+	))
	1420	+	.unwrap();
	1421	+	st.materialize();
1035	1422		}
1036	1423
1037	1424		/// Version 2 payloads (spec §11): small graphs inline, large ones by
		…	158 unchanged lines

History-only states: log, log of a path and blame_in load changes and tree only, deferring file edits; load_graphs builds the graphs a command needs from checkpoint blobs or by replay, identical to a full load; an unloaded graph is never read as empty e8d38e47e9d7

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