Commit Graph
43 Commits
Author SHA1 Message Date
claudeandClaude Fable 5.1 07ba53ca79 fix(prune): reclaim merged branches, and size the volume for the clone
Two assumptions in the eviction pass did not hold on this forge, and
between them a volume filled up three times in three days with nothing
reclaimed automatically. Both are replaced here; the pass also moves
ahead of the seed, which is the only order in which its work can help
the run performing it.

LIVENESS. Pass 1 evicted a cache only when its branch was gone from
origin. Gitea keeps a PR's branch after the merge unless the repo opts
into delete-on-merge, and zemyna does not — so ls-remote reports fifty
merged branches and the signal fires for none of them. A second signal
is added beside it: a branch still on origin whose tip is an ancestor of
a protected branch's tip holds no commit that branch does not, so its
cache will never be read again and goes in the same unconditional pass.

Ancestry is answered from the commits in the job's own checkout, so the
answer "cannot tell" exists and stays distinct from "not merged" at both
granularities. A shallow checkout withholds the signal entirely, since a
missing object is its normal case rather than evidence. A single branch
whose tip is not in the checkout is kept, with a warning naming it. A
squash or rebase merge leaves no ancestry and reads as live until the
branch is deleted. All three are missed reclamations, which cost disk;
the other direction costs a branch its cache mid-build.

HEADROOM. Passes 2 and 3 gated on a percentage of the volume, which
cannot express the failure they have to prevent: a clone runs out of
disk while unsharing its mutable paths, and how much that needs is a
property of the snapshot rather than of the disk. Staging failed at 34 G
free and passed at 74 G, so a 10% floor — 19 G here — never fired first.
The requirement is now measured per run off the very source the seed
will read, the pass evicts oldest-first until it is met and stops there,
and falling short of it fails with the shortfall and every directory it
kept, rather than letting the seed fail seconds later against a staging
path that names none of that. min-free-percent survives as an additional
floor, defaulting to 0, and falling short of that one is still a warning
and a self-clear.

ORDERING. The prune step ran after the seed, so each run freed space for
the next one. It now runs between resolve and seed. Two things that
makes newly reachable are closed: the source about to be cloned is
excluded from every pass by name, and a concurrent job's target dir
already carries its lock from the instant it appears under its final
name, so nothing is seen unlocked that is in use.

Red-proven: sixteen assertions across the four new scenarios fail
against the pre-fix scripts, including the zemyna layout evicting
nothing where it should evict exactly one directory, and the headroom
scenario exiting 0 where it should exit 1.

Refs #20.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JXMQCJ5Eg5f9G9cfYzyh4Z
2026-09-07 00:21:12 -05:00
claudeandClaude Fable 5.1 a960c8f91b refactor(cache): name the mutable set once, and measure it
The set of paths a hardlink clone has to real-copy — dep-info,
build-script metadata, linked outputs, the pruned directories that hold
them — was spelled out inline in unshare_mutable_paths, in four find
invocations. Nothing else needed it, so one spelling was enough.

Something else needs it now: the prune has to know what a clone will
cost before it happens, and a sizer with its own copy of the predicates
would drift from the copier silently and in the dangerous direction — an
under-measured clone is one that starts and runs out of disk halfway
through unsharing. So the directory names become one array and the file
rules one dispatcher, applied by a callback per side, with each rule's
rationale moved to the rule rather than left at the old call site.

mutable_set_kb measures that set off a snapshot, skipping the subtrees
already measured whole so nothing is counted twice; clone_headroom_kb
scales it by a hand-written margin and floor for what the measurement
cannot see (cp -al materialising every directory for real, and the
unshare holding one subtree twice at its peak). Both residuals are named
where the function is, in both directions.

seed_source_candidates moves the seed's source-preference list into
cache-lib for the same reason: the prune ahead of it has to resolve the
same source the seed will clone, and two agreeing derivations are one
edit away from disagreeing.

No behaviour change — the copier applies the same rules to the same
tree, verified by the hardlink-clone suite's inode partition in both
directions.

Refs #20.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JXMQCJ5Eg5f9G9cfYzyh4Z
2026-09-07 00:20:45 -05:00
claudeandClaude Opus 5 5abd0a9968 docs(ci): name the timing fields this forge actually returns
CI / shellcheck + selftests (pull_request) Successful in 1m30s
The accepted-cost derivation cited `run_started_at` and `updated_at`, which are
GitHub's field names. This Gitea's runs payload has neither -- it returns
`started_at` and `completed_at`, and omits `run_started_at`, `updated_at` and
`created_at` entirely (confirmed by dumping the keys of a run object). The
figures are unaffected: the script that produced them fell through to the real
fields, so 83 s median over 77-106 s stands.

The derivation was named so a reader could re-take the measurement, and as
written it returned nothing when followed literally, which defeats the only
reason it was there.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LjbhSqQf3pwnPA6MVaWcWL
2026-09-02 13:03:45 -05:00
claudeandClaude Opus 5 8217f53d4a docs(ci): measure the accepted cost instead of comparing it unmeasured
CI / shellcheck + selftests (pull_request) Successful in 1m21s
The accepted-cost paragraph claimed this repo's job made the `edited` trade
worse than in the sibling repos that shipped it first, reasoning from the
toolchain install, the Cargo-driving suites and `timeout-minutes: 20`. The
measurement inverts it: last twelve non-skipped runs here are 83 s median
(77-106), against ~118 s for daniel/gitdan and ~330 s for daniel/emowheel --
this is the cheapest of the three, and 20 minutes is a hang ceiling, not a
duration. This PR's own runs measured 87 s and 90 s.

The comparison is dropped rather than re-pointed; the absolute figure replaces
it, with the derivation named (`run_started_at` to `updated_at` off the Actions
API) so a reader can re-take it. The neighbouring concurrency claim was read
off this repo's own file and is unchanged -- it was the checked half of a
paragraph whose other half was not.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LjbhSqQf3pwnPA6MVaWcWL
2026-09-02 12:55:24 -05:00
claudeandClaude Opus 5 5b6acd7b3b docs(ci): date the cancellation observation to 1.26.0, not the current version
CI / shellcheck + selftests (pull_request) Successful in 1m30s
The concurrency note said "this Gitea (1.26.0)" while `GET /version` now
returns 1.27.2 — the instance was upgraded on 2026-08-25/26 (daniel/gitdan's
runbook, gitdan#46). Swapping the number would have asserted the cancellation
was observed on 1.27.2, which nobody has checked: the runs it cites were seen
before the upgrade. The comment now dates the observation to 1.26.0, names the
current version, and says persistence is unverified — which is why every commit
gets its own group rather than trusting `cancel-in-progress`. That reasoning is
unchanged; only the implied currency was wrong.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LjbhSqQf3pwnPA6MVaWcWL
2026-09-02 12:49:56 -05:00
claudeandClaude Opus 5 b791896e03 fix(ci): trigger on edited so un-drafting actually lifts the draft skip
CI / shellcheck + selftests (pull_request) Successful in 1m27s
`ready_for_review` does not exist as a pull_request action on this Gitea, so
it never fired and the draft skip never lifted: a PR opened as `WIP:` carried
its skip decision to merge unless a later push happened to create a run. Draft
here is not a persisted column — it is the `WIP:` title prefix, derived by
`issue.IsWorkInProgress` — so un-drafting is a title edit, which fires a plain
`edited`.

Ported from daniel/emowheel commit 08da820 (see daniel/emowheel#71) and
daniel/gitdan (see daniel/gitdan#92), where the identical change landed first.

Accepted cost: Gitea populates no `changes` field for a title-or-body edit, so
the workflow cannot tell an un-drafting edit from an ordinary body PATCH, and
every body edit on a non-draft PR now starts a real run. That is a heavier
trade here than in the sibling repos -- this job installs two Rust toolchains
and drives a real Cargo, at `timeout-minutes: 20` -- but the `concurrency:`
block groups `pull_request` runs on `github.ref` with `cancel-in-progress:
true`, so a burst of edits collapses to one run. Still-draft PRs are unchanged.

Docs: the workflow comment is rewritten and shortened, and README's Development
section retires the empty-commit workaround it prescribed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LjbhSqQf3pwnPA6MVaWcWL
2026-09-02 12:34:24 -05:00
claude 4bb880b7a7 chore(ci): trigger CI after un-WIP
CI / shellcheck + selftests (pull_request) Successful in 1m21s
2026-08-27 14:52:11 -05:00
claude fb3c72aa28 docs(hardlink): withdraw the nlink claim, which asserted more than was measured
CI / shellcheck + selftests (pull_request) Skipped
The comments said hardlink count at link time was ruled out as the
discriminator between a rewritten executable and an intact one, citing a
lib+bin crate whose two test binaries were both `nlink == 1` and appeared to
behave differently. Re-checked on review: the intact one had not been rebuilt
at all — same content, same inode — so it demonstrated nothing, and forcing
both to rebuild rewrote both.

What was actually observed is narrower and now says so: every executable
measured intact had an uplift hardlink twin Cargo must re-create anyway, every
one measured rewritten had none, and whether the twin is the mechanism or a
correlate was not determined. The rule does not rest on the answer — exempting
twinned executables would recover none of the bytes this change newly copies.

This PR exists because a claim outlived its evidence; it should not ship one.
2026-08-27 14:50:53 -05:00
claude 0553a6b956 fix(hardlink): resolve an ambiguous out/ toward unsharing, and pin the linked-output scenario on a shape that exhibits it
CI / shellcheck + selftests (pull_request) Skipped
Two review findings on #16.

The `out/` discriminator keyed on Cargo's record of a build-script execution,
which Cargo writes only AFTER the script exits successfully. A build script
that populates OUT_DIR and then fails leaves a unit with no record at all, so
its OUT_DIR read as a compile unit's artifact directory and stayed shared —
a regression against the old `-name build` selection, which real-copied that
state by construction. Reproduced on cargo 1.93.1 stable.

An `out` directory now stays shared only when two independent signals agree:
it holds an `.rlib`/`.rmeta` of its own, and its unit carries no execution
record. Either one missing real-copies it. The cost is unchanged to the byte —
the newly-unshared directories hold only executables and `*.d`, both already
privately owned by the file rules.

The live linked-test-binary scenario was built on the lib+bin probe crate,
whose test binaries relink to a fresh inode — a shape gitdan-actions#17 records
as measured safe. Both halves passed green against the unfixed selection on
dep-info mutations the previous scenario already covers. It now builds a
bin-only crate with a unit test, reads only executables, and skips loudly with
a warning rather than passing quietly if the toolchain does not exhibit the
rewrite at all.

Also: drop a clause asserting the linker writes in place "whenever the path has
no other hard link", which this change's own evidence denies; move the
load-bearing comment block back above `unshare_mutable_paths`; correct a
superseded 99.998% figure; and record both cost rows in the README rather than
only the flattering whole-tree one.
2026-08-27 14:39:29 -05:00
claude e5b26a9368 fix(hardlink): name the mutable set directly, under both build-dir layouts
CI / shellcheck + selftests (pull_request) Skipped
`unshare_mutable_paths` selected `.fingerprint` and `build` directories. Under
Cargo's build-dir layout v2 the first clause matches nothing and the second
matches the whole tree, because v2 regroups artifacts under `build/` alongside
the metadata. Measured on one scratch crate: 39.3% of the tree real-copied
under v1, 99.996% under v2.

The selection now names the mutable set rather than the container it used to
live in: fingerprint directories under either spelling, layout v2's `run/`
directories, layout v1's loose build-script run metadata, and the `out`
directories that are a build script's OUT_DIR rather than a compile unit's
artifact directory. The two are told apart structurally, by Cargo's record of
the build-script execution sitting beside the OUT_DIR and nowhere else.

Verifying that turned up a second, layout-independent hazard: a linked
executable is written through whatever inode is already at its path, so a
`cargo test --no-run` inside a `cp -al` clone rewrites the source's own test
binary. Reproduced on cargo 1.93.1 stable, 1.96.0-nightly, 1.98.0-nightly and
1.100.0-nightly, under both layouts. Every executable is now real-copied;
`.rlib`, `.rmeta` and `incremental/` are what stay shared.

hardlink-clone-selftest.sh gains two file-only layout fixtures that pin the
partition in both directions without a compiler, and a live scenario that
relinks a test binary.
2026-08-27 14:12:01 -05:00
claude fa3cef53e0 docs(ci): the nightly does enable content freshness, as of 2026-08-26
CI / shellcheck + selftests (pull_request) Successful in 1m36s
The README's CI section still described the nightly toolchain step as
buying nothing: "which no nightly currently enables, so it is skipped and
the step is kept only against the day upstream restores it". That
sentence predates this branch and states as fact the exact reading the
rest of the PR retracts.

Three things in this PR falsify it. The corrected `env:` block at
README.md:110-117 records that since cargo PR #17382 (2026-08-22) the
`-Z` gate only unlocks the feature and `build.fingerprint` selects it, so
setting both turns it on. The corrected workflow comment in
.gitea/workflows/ci.yaml says "as of 2026-08-26 it does". And this
branch's own CI run printed `=== checksum-freshness mode: on ===` and
`hardlink-clone-selftest: 4 assertions passed` on 1.100.0-nightly
(787af2b8c 2026-08-25) — the scenario is not skipped, it runs.

The paragraph also carried no date, which is the failure mode every other
block this PR touched was rewritten to prevent. The replacement is dated
and names the toolchain, matching the corrected blocks elsewhere.

It deliberately stops short of "the scenario always runs": the suite
still settles the question by experiment on every run and still skips
loudly when it cannot measure, so the step is not unconditionally
exercised. Saying otherwise would trade one overclaim for its mirror.

Docs-only; no behaviour change.
2026-08-26 20:02:02 -05:00
claude 554310186f fix(hardlink): content freshness moved switches, it was not withdrawn
CI / shellcheck + selftests (pull_request) Successful in 1m17s
`unshare_mutable_paths`' comment recorded that upstream had stopped
rewriting `dep-<target>` in place, on a measurement taken against
1.100.0-nightly. It had not. Two unrelated cargo changes landed within
four days of each other and between them moved the switch that turns the
behaviour on and the path it writes to:

  - cargo PR #17382 (2026-08-22) demoted `-Z checksum-freshness` to a
    gate and gave `build.fingerprint` the choice, defaulting to `mtime`.
    Setting only the gate is accepted and does nothing, which is exactly
    the result that was read as a withdrawal.
  - build-dir layout v2 (cargo PR #17354, stable 1.100.0 on 2026-11-12,
    nightly default since 1.99) moved the file from
    `.fingerprint/<unit>/dep-*` to `build/<pkg>/<hash>/fingerprint/dep-*`.

Measured 2026-08-26 on 1.100.0-nightly (e8cb624d5): same toolchain, same
clone procedure, one env var apart — with the gate alone a `cp -al` clone
mutates only the build/ and *.d families; add
`CARGO_BUILD_FINGERPRINT=content` and the source's dep-info file is
mutated through the shared inode again. The hazard is intact.

So the suite now exports both switches, and its strongest scenario runs
again on current nightlies — verified passing against both layouts. Its
control note learned the v2 path too: it looked for the v1 path only, and
so printed "does NOT rewrite ... in place" three lines beneath a listing
that showed the rewrite.

Every claim these comments make is now dated and cited, because the
defect being fixed is a comment that cited one measurement and silently
stopped reproducing.

Layout v2 also drags the artifacts under `build/`, which collapses this
function's real-copy set from 21.3% of a target dir to 99.998%. That is a
live cost, not a correctness problem, and it is filed as gitdan-actions#14
rather than fixed here.

Part of daniel/gitdan#62.
2026-08-26 19:48:07 -05:00
claude e94c46f2ec test(hardlink): move the probe's INACTIVE answer off bash's error codes
CI / shellcheck + selftests (pull_request) Successful in 1m21s
Review finding on #13, and the last change to this function. A typo'd variable
name on a line that HAS its `|| exit 2` guard — `$CONTNET_B` for `$CONTENT_B`
— fails in EXPANSION, before the command runs, so neither the guard nor the
ERR trap ever sees it. Under `set -u` that exits 1, which was the code meaning
"measured, and the answer is mtime". Not a live defect: the probe references
only set variables today, and the 1 gitdan-ci reports is a genuine measurement.

The defect is that the answer codes and the error codes overlapped at all.
Three rounds on this function each found a narrower way for a shell-generated
1 to be read as a measurement — an unguarded command, then a guarded line
whose guard could not fire — and each was closed by narrowing the failure
surface, which is a game with no last move.

INACTIVE is now 3, and anything that is not 0 or 3 is NOT MEASURED. Bash
generates 1, 2, 126, 127 and 128+n for its own errors and never 3, so "not an
answer" is decided by a property of the shell rather than by an enumeration of
the ways a step can go wrong. A step added later without a guard, or with a
guard that cannot fire, lands on NOT MEASURED by construction.

The guards and the trap stay, with their job restated: reporting rather than
correctness. They put a failed step on 2 with both probe logs printed instead
of on some incidental status — nicer to debug, and the same destination either
way. The `set +e` bracket at the call site keeps its own note, since a `set -e`
that cannot fire is the kind of thing a reader assumes works.

The not-measured message now quotes the actual exit code, so the two ways to
reach it are distinguishable in a log without reading this file.

Red-proven with the reviewer's own mutation, A/B: with INACTIVE at 1 the typo
reports `mode: off — resolves freshness by mtime`, a false measurement; at 3 it
reports `mode: unmeasured — the probe exited 1`. All four paths re-verified —
unmodified 4 assertions; env stripped inside the probe, measured INACTIVE with
the mtime reason; a broken probe build, unmeasured via a guard; an unguarded
`false`, unmeasured via the trap.
2026-08-26 14:40:27 -05:00
claude 5b46986cd7 test(hardlink): make the errexit invariant real, and stop gpg deciding a gate
CI / shellcheck + selftests (pull_request) Successful in 1m23s
Two review findings on #13.

THE STATED INVARIANT WAS NOT IN FORCE. The header claimed a `set -e` abort
could never be mistaken for the `1` that means "measured, and the answer is
mtime". It could not fire at all: `checksum_freshness_probe || probe_rc=$?`
runs the left side with errexit suppressed, and that suppression propagates
into the subshell. An unguarded step there fell through to `exit 0` and
reported ACTIVE — a fourth outcome the header said was impossible. The guard
audit was complete, so nothing was broken; the wrong mechanism had the credit,
in a comment inviting the next editor to add an unguarded step and rely on it.

The suggested fix — `set -e` as the first line of the subshell — does not work,
and measured on bash 5.3 it makes things worse rather than not-better:

  set -e inside a subshell called via `||` or `if`   still falls through: rc=0
  set -e inside, called with errexit off at the site aborts, but with the
                                                     FAILING COMMAND's status —
                                                     `false` gives 1, which is
                                                     exactly the value that
                                                     means "mtime"

So both halves are needed and neither is decoration: `set +e` around the call
site, so the subshell can arm its own errexit at all, and `trap 'exit 2' ERR`
inside it, so an abort lands on "not measured" instead of on an answer. The
explicit `|| exit 2` guards stay as the first line of defence. All of that is
now written down where the false claim was.

Red-proven with one unguarded `false` between the `touch` and the second
build, on a box where freshness is live: without the fix, mode `on` and 4
assertions — the reviewer's fourth outcome, reproduced; with it, mode
`unmeasured`, the warning, 3 assertions; unmodified, mode `on` and 4.

Recorded in the same block, since the next person to hit a `2` will ask: why it
skips rather than fails. The gated scenario is the only thing here that depends
on freshness mode, and failing would turn a statement about one machine into a
red gate reading "the hardlink scheme is broken" across three consuming repos.
What would change the answer is `2` becoming the everyday CI outcome, and run
2583 measures that it is not — gitdan-ci reports `1`.

GPG. The two suites that commit in scratch repos inherited the developer's
GLOBAL `commit.gpgsign`, so whether this gate passes could depend on their gpg
agent — seen as a red `restore-mtimes-selftest.sh` caused by a full disk
breaking gpg, in a suite with nothing to say about either. Pinned off locally,
in the throwaway repos only: `git config commit.gpgsign false` beside the
identity the scratch repo already sets, and `-c commit.gpgsign=false` on
prune-cache-selftest's three commits, matching its existing `-c` style.
Red-proven under a GIT_CONFIG_GLOBAL with gpgsign on and a nonexistent gpg
program: without it `fatal: failed to write commit object`, with it both
suites pass.
2026-08-26 14:28:22 -05:00
claude 5a90d5c829 test(hardlink): let the freshness probe report that it could not measure
CI / shellcheck + selftests (pull_request) Successful in 1m21s
Review finding on #13. `checksum_freshness_active()` returned non-zero for any
reason — including its own `cargo build` failing — and the caller's `else`
branch then announced "this nightly accepts -Z checksum-freshness but still
resolves freshness by mtime" regardless. On a machine where content freshness
IS live, breaking only the probe's build produced that sentence, which is
false, and silently dropped the scenario, which is lost coverage. Reachable,
not theoretical: it needs a half-installed toolchain, which is exactly the
state a probe exists to notice.

The whole point of the preceding commit was to settle this by experiment
rather than by asking, and an experiment that cannot tell a negative result
from a failed measurement is not settling it. "This toolchain resolves
freshness by mtime" is a statement about Cargo; "a probe build failed" is a
statement about this machine. They are not interchangeable.

Three outcomes now, carried in an exit code:

  0  measured ACTIVE     both builds ran, the backdated rebuild recompiled
  1  measured INACTIVE   both builds ran, the backdated rebuild was Fresh
  2  NOT MEASURED        a probe step failed; nothing was learned

Every step that could fail for a reason other than the experiment's own
outcome exits 2 explicitly, so a `set -e` abort cannot be mistaken for the 1
that means "measured, and the answer is mtime". Outcome 2 emits a ::warning::
saying in those words that this is a failure to measure and not a finding
about Cargo, and prints the tail of both probe logs. The scenario still skips
for 1 and 2 alike — everything else the suite asserts is independent of
freshness mode — but the reason is now carried to the skip line, so the two
are distinguishable at a glance.

Verified all three states on a machine where freshness is live: unmodified,
mode `on` and 4 assertions; probe build broken with a bogus flag, mode
`unmeasured` with the warning and 3 assertions, and no claim about mtime;
CARGO_UNSTABLE_CHECKSUM_FRESHNESS stripped inside the probe — CI's condition —
mode `off` naming mtime, and 3 assertions.
2026-08-26 13:34:42 -05:00
claude eb3f0bd09b docs(ci): say what the nightly step actually buys today
CI / shellcheck + selftests (pull_request) Successful in 1m24s
The step's comment claimed nightly was not optional. CI's own first green run
falsified that: 1.100.0-nightly accepts -Z checksum-freshness and resolves
freshness by mtime regardless, so the suite's probe reports it and skips the
scenario either way.

The step stays — twenty seconds, and the coverage returns by itself the day
upstream restores the behaviour — but the comment now says that rather than
the opposite. The open question about what upstream actually did is
daniel/gitdan#62.
2026-08-26 12:57:15 -05:00
claude 6a80423bd0 test(hardlink): settle checksum freshness by experiment, not by asking
CI / shellcheck + selftests (pull_request) Successful in 1m17s
Third toolchain probe in this branch, and the first one that asks the
question the suite actually depends on. The two before it each let the suite
assert a property the toolchain did not have:

  cargo +nightly -V                    answers "did a proxy called with
                                       +nightly exit 0". `-V` short-circuits
                                       before `-Z` is parsed at all.
  cargo +nightly -Z checksum-freshness answers "is the flag still accepted".
   locate-project                      1.100.0-nightly (2026-08-25) accepts it
                                       and resolves freshness by mtime anyway,
                                       which is how CI reached the final
                                       scenario and failed there.

The final scenario depends on exactly one property: that changed content with
an OLDER mtime rebuilds. Under mtime freshness the correct answer is Fresh, so
under mtime freshness that scenario asserts a bug — which is what CI reported.

So the probe performs that experiment, on its own crate and its own target
dir, with no clone anywhere near it. That separation is also what keeps it a
control rather than a restatement: the probe establishes that the toolchain
rebuilds on content, the scenario establishes that a hardlink clone did not
take that away.

Verified both ways locally: with a real content-freshness nightly, mode on and
4 assertions; with the env var stripped inside the probe — the runner's
condition, faithfully — the probe says so by name, mode goes off, the scenario
is skipped loudly and the remaining 3 assertions pass.
2026-08-26 12:54:24 -05:00
claude 5e8e773f78 test(hardlink): report the mutation families, don't assert one of them
CI / shellcheck + selftests (pull_request) Failing after 1m21s
CI's nightly is 1.100.0-nightly (2026-08-25); the machine this suite was
written on had 1.96.0-nightly (2026-02-24). On the newer one the control's
`cp -al` clone mutates only the build/ and *.d families — upstream appears to
have stopped rewriting `.fingerprint/*/dep-*` in place under checksum
freshness — so the suite went red on the *absence* of a hazard.

That is the wrong shape for a gate. The control's job is to prove the hazard
exists at all, which a non-empty mutated set already does; naming one family
as mandatory makes the suite red whenever upstream stops doing something we
never wanted it to do, and red in the CONTROL, where a failure reads as "the
hazard is gone" rather than "upstream changed". It is now a note either way.

Nothing is given up. The fix scenario asserts the source is byte-identical
after a full rebuild in the clone, which covers every family the running Cargo
has, named or not — and the checksum-freshness scenario after it tests the
stale-reuse hazard directly. The dep-* line only ever documented which family
was in play.

`unshare_mutable_paths` keeps unsharing dep-* regardless, and its measurement
block now records both observations with their versions: 22 MB of a 6.9 GB
tree against a failure mode that is a wrong answer rather than a slow one.
2026-08-26 12:50:42 -05:00
claude 3f97d3d1e7 fix(selftest): make the two compiler-backed suites survive a CI runner
CI / shellcheck + selftests (pull_request) Failing after 1m36s
The new gate's first run went red on both suites that drive a real Cargo.
Neither failure was a defect in what they test; both were assumptions about
the machine, which had only ever been a dev box with a nightly installed and
no colour forcing. Fixed here rather than waived — turning a gate on is what
obliges fixing what it finds.

COLOUR. Every assertion in restore-mtimes-selftest.sh, and one in
hardlink-clone-selftest.sh, reads cargo's own words out of a build log
(`Compiling libdep`, `Fresh probe`). gitdan-ci's runner image forces colour, so
cargo wrote `Compiling\e[0m libdep` into the log and `grep -q "Compiling
libdep"` stopped matching. The suite then reported the opposite of what
happened — the failure printed the log, and the log plainly said `Compiling
libdep`. Both suites now pin CARGO_TERM_COLOR=never, which is the format their
assertions are written against.

Red-proven: with the export removed and CARGO_TERM_COLOR=always,
restore-mtimes-selftest reproduces the CI failure verbatim ("expected to find:
Compiling libdep"); with it, 14/14 pass under the same forced colour.

THE NIGHTLY PROBE ASKED THE WRONG QUESTION. `cargo +nightly -V` answers "did a
cargo proxy called with +nightly exit 0", which is not "will this build have
checksum freshness": `-V` short-circuits before `-Z` is validated at all. So
the probe said "on" on a runner where the flag was not in effect, and the
suite asserted the checksum-freshness mutation family against a build that
never had it — failing in the CONTROL, where a failure reads as "the hazard is
gone" rather than "the toolchain is wrong". It now probes the capability:
`cargo +nightly -Z checksum-freshness locate-project`, the narrowest command
that actually parses the flag. It rejects the stable channel and an unknown
flag name alike, needs no network and builds nothing.

Red-proven: the old channel probe, pointed at a cargo without the flag,
reproduces the CI failure exactly.

AND THE OFF PATH DID NOT WORK EITHER. The suite's header claimed that without
checksum freshness "the test still covers the build/ and *.d families". It did
not: the final scenario backdates the source to 2001 and asserts the rebuild
is not Fresh, which is checksum-freshness-only reasoning. Under Cargo's
ordinary mtime freshness a 2001 source IS older than the artifact and Fresh is
the correct answer, so the scenario asserted a bug. It is now gated on the
mode and skipped loudly, like the control's dep-* assertion already was: 5
assertions with a nightly, 3 without.

CI installs a nightly as well as stable (nightly first, so stable stays the
default) — that hazard is the one this whole scheme exists to close, and a CI
that skips it is checking the cheap half.
2026-08-26 12:46:03 -05:00
claude fb7a788c90 feat(cache): give same-ref jobs separate build directories via cache-lineage
CI / shellcheck + selftests (pull_request) Failing after 1m19s
A cache key names a REF. What a target directory holds is the product of a ref
and a build configuration, and emowheel builds the same ref twice on every
push — once for the host, once for wasm32, in two jobs that start together.
Keyed on the ref alone, `cargo-cache@v1` handed both the same
CARGO_TARGET_DIR, and Cargo's target-directory lock is exclusive: the second
job sat on "Blocking waiting for file lock on build directory" for the length
of the first while holding a runner capacity slot, so a third repo's queued
job waited behind a job doing nothing.

`cache-lineage` is that second dimension. It names ONE directory level under
the cache root:

    <cache-root>/target-<key>              no lineage (unchanged)
    <cache-root>/<lineage>/target-<key>    a lineage

Nesting, not a suffix on the key, and that is the whole design decision.
`prune-cache.sh`'s liveness pass classifies a directory by recomputing
`target-<cache_key(branch)>` for every branch on origin and evicting whatever
does not match — a `target-<key>-wasm32` matches nothing, so it would be
classified dead and evicted unconditionally on every run. daniel/gitdan's
host-level arbiter reads the same shape (BRANCH_DIR_RE); a suffixed name falls
out of that too, so those caches would never be reclaim candidates and a whole
lineage would go missing from the shared disk budget. Nesting leaves both
matchers reading exactly the names they already read, one level down — which
is a layout that arbiter already walks (CI_CACHE_MAX_DEPTH is 2, and its own
suite pins the depth-2 case).

Every interacting part, checked rather than assumed:

- SEED: `seed-target-dir.sh` takes the root as an argument, so a PR branch in
  a lineage layers over THAT lineage's base snapshot. Asserted.
- PUBLISH: `publish-snapshot.sh` derives both ends of the swap from the root.
  The publish action now takes the root from the `CARGO_CACHE_ROOT` the
  consume step exported, and CHECKS its own inputs against it — a publish step
  left at the default while its consume step nested would otherwise republish
  a different lineage's live target dir over that lineage's snapshot, on every
  push, silently. `mode: release-lock` is exempt: it releases a lock on
  `$CARGO_TARGET_DIR` and never touches a root.
- WATERMARK: per target dir, so it follows the lineage. Unchanged.
- PRUNE and LIVENESS: scoped to the root they are given, so a pass in one
  lineage neither evicts nor sees a sibling's caches, or the flat layout's.
  Liveness keeps resolving real branch names, which is what a key suffix would
  have broken.
- ci_cache_reclaim: verified by dry-run against a fixture in this layout —
  all six nested and flat dirs collected as candidates, protection resolved
  correctly on the nested ones, and a `.stage-` stranded inside the lineage
  found by the leftover sweep.

Refused lineage names are refused at resolve time, each rejection naming the
reader that imposes it: a path separator (the arbiter's depth budget), a
Cargo profile name (its no-descend list), a `target-`/`snapshot-` prefix (this
repo's own prune globs), a hex suffix (its per-branch-dir shape), a dot prefix
(the leftover-naming contract). None of these fails visibly on its own — each
produces a working directory that some pass silently stops seeing.

Setting no lineage resolves to the cache root byte for byte, so lublub, zemyna
and emowheel's `ci` job keep the exact directories they have on the volume.

New suite `cache-root-selftest.sh` (19 assertions), red-proven against three
deliberate breakages: a `cache_root_for` that ignores the lineage, a disabled
validator, and a `verify` that never rejects a mismatch.
2026-08-26 12:32:21 -05:00
claude f76789358d ci(gitea): gate scripts/ with shellcheck and the selftests
This repo had eight scripts, six selftest suites and nothing that ran any of
them. It is a composite action consumed at `@v1` — a moving tag — by three
repos' CI, so a bad edit here reaches zemyna, emowheel and lublub at once and
is discovered by whichever of them builds next.

One job: `shellcheck -x --source-path=scripts scripts/*.sh`, then
`bash scripts/selftest.sh`. `-x` follows the `. cache-lib.sh` every script
sources, which is where most of the logic being checked lives; without it
shellcheck reports SC1091 and analyses each file with a hole in it.

The full suite, not `--fast`: `hardlink-clone-selftest.sh` and
`restore-mtimes-selftest.sh` are the two that drive a real Cargo rather than a
fixture, and selftest.sh's own header says `--fast` is for iterating, not for
signing off a change. So the job installs a stable toolchain. The scratch
workspaces they build use path dependencies only, so nothing reaches
crates.io, and the job references no credentials at all.

Modelled on daniel/gitdan's workflow, including the two clauses of the
draft-skip guard (`github.event_name != 'pull_request' ||
!github.event.pull_request.draft` — the first is what stops the second from
also skipping pushes to `main`, where there is no `pull_request` context) and
the per-commit concurrency group for `push`.

No `container.volumes:` entry, deliberately: the suites want a cold target dir
every run, since "did this rebuild?" is exactly what restore-mtimes-selftest
asks. This job takes no share of the shared CI cache disk budget.

Turning the gate on surfaced three pre-existing findings, all fixed here
rather than suppressed or waived:

- `restore-mtimes-selftest.sh` SC2038: `find | xargs touch` -> `-print0 | xargs -0`.
- `hardlink-clone-selftest.sh` SC2295: `${f#$base_fix/}` -> `${f#"$base_fix"/}`.
- `cache-lib.sh` SC2016: a per-line disable with the rationale. The single
  quotes are load-bearing — the program is for the inner shell, where `$f` is
  its loop variable, `$rc` its accumulator and `$$` its pid — so this is the
  documented-false-positive case, not a stopgap.
2026-08-26 12:31:50 -05:00
claude 1aca90b461 test(seed): pin reader_lock_acquire in hardlink_clone_into (#12)
Co-authored-by: Claude <claude@gitdan.com>
Co-committed-by: Claude <claude@gitdan.com>
2026-08-24 23:05:18 +00:00
claude df6f1b91fb docs(cache): producer half of the depended-upon names contract (#11)
Co-authored-by: Claude <claude@gitdan.com>
Co-committed-by: Claude <claude@gitdan.com>
2026-08-24 23:03:29 +00:00
claude 31b4113a26 docs(readme): drop an ordering claim scenario 9 does not make
The previous wording said the unshare pass aborts the clone "before the copy's
own exit status is ever consulted", which describes neither version. Unmutated,
the status is consulted immediately after the copy and fires first, so the
unshare pass is never reached; mutated, there is no check left to consult at
either point. As written a reader could take it for a claim that
unshare_mutable_paths runs before the torn-clone condition inside
hardlink_clone_into, which is the kind of ordering this file is otherwise
careful to state exactly (see the reader-marker ordering proof it sits under).

Names the mutation instead: deleting the exit-status check does not change the
outcome, because the unshare pass aborts the clone in its place. The mechanism
is unchanged and still holds — `cp -al` over a mode-000 source creates the
destination preserving mode 000 before failing, and `find | xargs` over that
returns 1 under pipefail, which _unshare_files propagates.
2026-08-24 14:28:08 -05:00
claude eb7878b822 docs(readme): correct the scenario census and the #5 citation
Review of #9 found the methodology section falsified by that PR and owned by
nobody — the scoping that fenced it off was wrong, #8 never touches these
paragraphs.

Three fixes:

* The PATH-stub paragraph named 8a and 8b as the seed suite's stubs. It is now
  four scenarios on two commands: 8a/8b/8c stub `cp` at the clone, 10 stubs it
  one level down at the per-file unshare, and 8d stubs `stat` — a mechanism
  the paragraph did not mention at all, and the only way to make an identity
  that could not be READ the sole witness.

* The assert-which-guard-fired paragraph cited issue #5 as a live example of a
  surviving mutation. #5 is the issue this PR closes, so a reader following
  that citation landed on "removing it leaves every suite green", which is no
  longer true. Scenario 9's own sentence stands — the matrix confirms it
  survives every mutant — so it now says WHY it survives (an unreadable source
  leaves the staging dir at mode 000, and the unshare pass aborts the clone
  before the copy's exit status is consulted) instead of citing a closed
  issue.

* Added the mutual-masking hazard the sweep turned up, since it is the general
  lesson rather than a fact about two particular terms: two guards that can
  each catch the same fault make each other unnecessary, so no fixture built
  around that fault pins either one.

Also names scenario 8d for what it is in its own comment — a regression guard
on a defensive term, not a reproduction of a reachable state. Every route to
the state it constructs is closed off (a rotation hands the witness to 8a, a
genuinely absent source hands it to 8c), which is the reason it is worth
pinning rather than a reason to doubt it.
2026-08-24 14:02:10 -05:00
claude bd60b430e0 test(seed): pin the two unguarded terms of the torn-clone condition
hardlink_clone_into's torn-clone detection is a four-term condition, and a
mutation sweep found two of the four unpinned: removing either
`[ "$cp_rc" -eq 0 ]` (issue #5) or `[ "$i_before" != missing ]` left all five
suites green. They were unpinned for the same reason — they mask each other.
A source that vanishes mid-clone reads as `missing` at both ends AND fails
`cp -al`, so with both terms present either one catches it and neither is
individually necessary.

Isolating them needs a state each term alone can see:

  8c  cp reports failure over a tree that is in fact whole. Neither inference
      sees anything — 0 entries short, one unchanged inode — so the exit
      status is the only witness. Forced with the PATH stub 8a/8b already
      use, on the consumer's own top-level clone.
  8d  both identity reads fail while the copy succeeds. `_dir_inode` folds
      every stat failure into the string `missing`, so two failed reads
      compare equal TO EACH OTHER; without the sentinel term the tree is
      published on the strength of two errors. Stubs `stat` narrowly — only
      the `%i` reads of this clone's own source — because taking the source
      away would fail `cp -al` too and pin 8c's property over again.

The sweep also found `_unshare_files`'s xargs status unpinned, which is the
guard that stops a staging tree whose dep-info files still point at the
SOURCE's inodes from being renamed into place — not a tear, so all four
clone checks pass it, and exactly the silent cross-branch stale-reuse the
scheme exists to prevent. Scenario 10 pins it by refusing the dep-info
unshares and asserting the clone discards rather than publishes.

assert_tear gains an `unreadable` identity expectation, and its `same` case
now demands a READ identity rather than two equal strings — `missing` equals
`missing`, which is the exact confusion 8d exists to pin.

Each of the five pinning scenarios was run in isolation against each
mutation; the result is a clean diagonal, so every scenario fails only for
its own term.

Closes #5
2026-08-24 13:24:53 -05:00
claude e3869c5920 docs(publish): address review nits on the contract block
Four corrections from the review of #8, all in the files this PR already
touches:

- A local signal on the line that creates .publish-new-. The other four shapes
  each got a note at their producing line, which is the whole premise of #7 —
  someone renaming TMP_DST reads its own comment block and would never see the
  contract note 45 lines up at OLD.

- '.publish-old- is milder' understated it. Milder is true; bounded is not. A
  key whose branch is merged, deleted or renamed is never published again, so
  its rotated generation stays until something outside this repo takes it —
  which is the case gitdan#30 itself makes, two lines away.

- The drift check now says the prefix constants ci-cache-reclaim.sh DECLARES,
  not the ones it enumerates. Those are different numbers: collect_entries()
  globs .stage- and .evicting- only, because .reading- is read and never
  swept. Only the declared reading makes the five-against-five count work, and
  a countability check that needs a coin flip to count is not one.

- publish-snapshot.sh's own header had two stale names ten lines above the
  stale pointer this PR fixes: step 1 staged at .stage-<tag> (that is
  hardlink_clone_into's inner path; the staged snapshot is .publish-new-<tag>)
  and step 2 named .publish-old-<tag> without the key. Pre-existing and
  outside both ACs, but #6's thesis is that a plausible-looking wrong name is
  the worst kind, and these are in the file the PR is about.

Comments and docs only. With comments and blank lines stripped, all three
scripts hash identically to origin/main.
2026-08-24 13:06:49 -05:00
claude 0118c28f01 docs(cache): state the .publish-* gap as a ticket, not a present state
The contract block asserted that neither side reclaims .publish-new- 'today'.
True when written and about to stop being true: gitdan#30 tracks adding both
.publish-* prefixes to the arbiter's enumeration, and a sibling track is
landing it this round. A comment that dates itself against a merge in flight
is worse than no comment.

Rewords all four sites (cache-lib.sh, publish-snapshot.sh, and README's table
row and prose) to reference gitdan#30 and keep the mechanism that made the
shape worth catching — .publish-new- is tagged per job per run exactly as
.stage- is — rather than the arbiter's momentary contents. The rule itself is
unchanged; it is the durable part, and it is what found this.

Adds the counting check while there: the five names here and the prefixes
ci-cache-reclaim.sh enumerates are meant to be the same length, so a mismatch
is the cheapest signal that one side gained a shape without telling the other.
2026-08-24 12:56:18 -05:00
claude 0cf6cc5973 docs(cache): write down the producer half of the leftover naming contract
daniel/gitdan's host-level arbiter (scripts/ci-cache-reclaim.sh) reclaims the
dot-prefixed trees this repo's scripts strand inside the cache volumes it
scans, and reads this repo's reader markers to decide whether one is still
live. That arrangement was documented only on the consuming side: a
contributor here could add or rename a dot-prefixed shape with no local signal
that anything outside the repo depended on the spelling, and the arbiter
enumerates by explicit prefix — deliberately, so it never sees a .reading-*
marker as a candidate — which makes an unannounced shape invisible to it
rather than conservatively handled.

Adds the producing side's half at the sites someone changing a name will
actually be looking at, pointing at gitdan's LEFTOVER NAMING CONTRACT block as
canonical rather than restating it:

- cache-lib.sh gains a header block naming every shape this repo creates under
  a cache root, its producing function, and how each strands; plus the rule
  that adding a shape obliges the same matching prefix over there as renaming
  one does.
- Site notes at .stage-'s and .reading-'s producing lines, and at
  .evicting-'s in prune-cache.sh.
- publish-snapshot.sh's .publish-old- / .publish-new- pair is documented as
  the shapes that are NOT in the arbiter's list today, with .publish-new-
  called out as the one that strands exactly as .stage- does and that neither
  side reclaims.
- The staleness direction: CACHE_READ_STALE_SECONDS and STALE_LOCK_SECONDS are
  mirrored there and the mirrors must be >= ours, because raising ours alone
  makes the arbiter delete a tree under an in-flight clone (its minimum-age
  guard does not back-stop that case). Lowering ours is safe in any order.
- README gains a short section a newcomer meets before adding a scratch
  directory under a cache root, cross-linked from the cache-layout block.

Comments and docs only; no behaviour change.

Closes #7
2026-08-24 12:50:07 -05:00
claude 1f42064d20 docs(publish): point the torn-clone note at the suite that reproduces it
publish-snapshot.sh's header described the silent-truncation failure mode as
the one "this script's own selftest (scenario 8)" reproduces. Wrong twice:
the scenario that reproduces a truncated clone is in
seed-target-dir-selftest.sh, and since #4 split the old scenario 8 into 8a and
8b it is 8b. publish-snapshot-selftest.sh does have a scenario 8 — the
abandoned-marker case — so the pointer landed on a real scenario with a
plausible number that tests something else.

Names the suite as well as the number, and says what the local scenario 8
actually is so the collision cannot re-form.

Closes #6
2026-08-24 12:49:53 -05:00
claude 0ee21bfbc8 docs(readme): census the three concurrency-scenario shapes honestly
Three corrections to the methodology paragraph, all of the same kind: it
stated as fact things that hold for some scenarios and not others.

"Run the real scripts as real concurrent processes" is true of seed scenario
7 and half-true of 8a; 8b, prune 12 and publish 6-8 spawn nothing. A reader
who stopped at that topic sentence would take away "spawn real concurrent
processes", which is the instinct that produced #3. The paragraph now leads
with the three shapes actually in use and says which scenarios take each:
a genuine race whose invariant holds under any interleaving; a PATH stub that
places the interference inside the window; and a synthetic stand-in for the
other side where the artefact is itself the contract.

That third shape — publish-snapshot-selftest.sh's held .reading-* marker —
was unmentioned, so the README implied that suite stubs something it does
not. Its own defence (the marker IS the contract between the two sides, and
racing a real slow consumer would make the suite's runtime the thing under
test) is a good reason and now sits beside the other two.

"Where more than one guard could catch a fault, the scenario asserts which
one did" was written as description when it is a target: seed scenario 9 does
not, which is exactly why #5's mutation survives it. Stated as the rule plus
its one live exception — a rule asserted as fact with a known counterexample
is the same defect as the sentence this paragraph replaced.
2026-08-24 12:04:35 -05:00
claude 5551e994da docs(readme): describe how the concurrency scenarios actually work now
README's Development section stated the repo's methodology for writing
concurrency scenarios as "gate the interfering step on observed progress of
the step it interferes with, so the window is hit deterministically". That
described the progress poll scenario 8 used, which this branch removes — and
the property it claims is precisely what issue #3 records as false: observing
that a walk has started says nothing about where it will be when the
interference lands.

Left standing it would tell the next contributor to build the next scenario
the way this one had to be rewritten. Replaced with what the suites do: stub,
on PATH, a command the code under test calls at a known point, so placement is
a fact rather than a scheduling outcome; assert the stub fired; and assert
which guard caught the fault where more than one could.

Also: the seed suite's table row now names both tear modes, and
publish-snapshot-selftest.sh's cross-reference points at 8a and 8b rather than
a scenario 8 that no longer exists. (publish-snapshot.sh's similar mislabel
predates this branch and is left alone.)

The stub directory and the real-cp lookup move up next to seed_with_stub, so
8b no longer depends on setup buried in 8a's block and either scenario can be
run or mutated alone.
2026-08-24 11:47:34 -05:00
claude dc0fef71f8 test(seed): force scenario 8's interleaving instead of racing for it
Scenario 8 started a real publisher once a consumer's clone was observed
past a fraction of the tree, then asserted the consumer ended up holding
the NEW generation. That premise is racy: when the publish lands after the
consumer's last identity read, the consumer legitimately completes a whole,
consistent generation 1 — and the assertion called that "the seeded tree is
truncated". The one gate this repo has was failing intermittently in the
most alarming direction available.

Replaced with two scenarios that place the interference deterministically,
the way prune-cache-selftest.sh scenario 12 places a marker inside the
check-to-unlink window: the consumer's own `cp` is stubbed, so whatever the
stub does happens strictly after hardlink_clone_into read the source's
entry count and inode and strictly before it reads that inode again.

  8a  the stub runs the real copy, then the real publish-snapshot.sh
      concurrently, and returns only once the swap is on disk. The copy
      succeeds and the staging tree is whole, so the source's identity is
      the only witness.
  8b  the stub renames a subtree out of the source's listing before the
      walk starts and back before the retry. The copy exits 0 and the
      source's identity never changes, so the entry count is the only
      witness — the silent truncation this whole guard exists for.

Each asserts WHICH of the clone's checks reported the tear (assert_tear),
so neither stays green if the check it exercises is deleted and another
happens to fire in its place.

Closes #3
2026-08-24 10:56:42 -05:00
claude b0d63c807b style(prune-cache): rewrap the settle-window comment; drop an overclaim
Review nits on #2, both cosmetic.

The sentence added last round left its paragraph at 127 characters in a file
that otherwise wraps comments at 78-79 — the rewrap after the insert simply
did not happen. `awk 'length($0)>80'` over both files now reports one comment
line, the pre-existing 93-character usage string at :4.

Scenario 14's header called its fixture "the only shape that can tell the two
timestamps apart". The property it needs is old mtime with fresh ctime; an
old directory renamed a moment ago is the production instance of that, not
the only construction of it. "Production's shape" was already carrying the
argument.

No behaviour change and no assertion change.
2026-08-24 09:10:43 -05:00
claude dcd73dd82d test(prune-cache): build scenario 14's aside the way the pass builds one
Review finding on #2. Swapping the settle window's `stat -c %Z` for `%Y` —
the exact substitution the comment beside it calls the wrong signal — left
the suite green at 37/37. The scenario built its aside with `mkdir`, so the
fixture's mtime was also ~now and the two timestamps agreed; a fixture whose
clocks agree cannot tell them apart.

Every real aside is the opposite shape: a cache last written days ago,
renamed a moment ago. Under `%Y` the window would never fire for one, the
sweeper would silently return to reclaiming asides another pass is still
deciding about, and nothing would say so — the mechanism guarded by a comment
again, which is what the previous finding was about.

So the fixture is now built the way the pass builds one: an old directory
`mv`d into the aside name. `%Z` -> `%Y` now fails scenario 14, as does
deleting the guard outright.

Also sharpens why the PID alternative was rejected: the `$$` in an aside's
name was that pass's PID inside its own job container, so testing it from
another one is not unreliable, it is meaningless.

No change to prune-cache.sh's behaviour; the assertions are untouched.
2026-08-23 23:46:03 -05:00
claude 65f0782233 fix(prune-cache): stop the aside sweeper depending on timing it cannot see
Review findings on #2. The first is the one that mattered: the sweeper this
PR added had the shape the PR exists to remove. Pass A renames a candidate
aside; pass B's sweep sees an aside with no readers and reclaims it; A then
finds a reader and restores. `rm -rf` traverses fd-relative, so the rename
does not stop it and A can republish a half-emptied tree under a live cache
name. `capacity: 1` bounds it today, which is exactly the kind of reason
this PR was written to stop relying on.

The unlink itself was never the problem — the ordering proof covers it under
any interleaving, since the aside name only exists after the evicting pass's
rename. What was missing is that an aside with no readers is indistinguishable
from one a pass has just created and not yet decided about. The sweeper now
leaves an aside alone until it has settled (EVICTION_ASIDE_SETTLE_SECONDS,
default 60), which separates the two without having to identify the pass that
created it — a PID is meaningless across the job containers these passes run
in, and recycles. Read from ctime, not mtime: rename(2) updates the first and
leaves the second at whenever the cache was last written, which is the signal
list_by_lru wants and the wrong one here.

That is a bound, not a construction, and both the code comment and the README
now say which of the two properties is which instead of asserting the broader
one.

Also from the review: a pass that declined every dead cache it found no
longer signs off with "no dead-branch caches found", and evict_dir no longer
promises a later reclamation of an aside that is already gone.

Scenario 14 covers the settle window against the script's own default, with
nothing faked — the directory really was set aside a moment ago. Scenario 4
gains the summary assertion. 31 -> 37 assertions; each new gate verified red
by defeating it alone in a scratch copy.
2026-08-23 23:30:56 -05:00
claude c6a3fa6d97 docs(readme): say who moves the v1 tag, when, and what it promises
The Versioning section named the moving-major-tag model but not the release
step that model implies. This is the first change where that gap has a
consequence: `v1` and `origin/main` are the same commit today, so merging
the eviction fix is the first thing that makes them diverge — at which point
the fix is on `main` and every consumer is still fetching the old scripts.

Records what was previously only implicit: that merging ships nothing, that
re-pointing `v1` is a deliberate post-merge action because it changes what
another repository's CI runs next, the exact commands and the check that it
took, what a consumer is promised by pinning `@v1` and what forces a `v2`,
and who is actually downstream. Also states why the moving pointer is the
right model here rather than immutable release tags, since "safer in
general" is the obvious objection and it deserves an answer.

Docs only; no script or action definition is touched.
2026-08-23 23:13:25 -05:00
claude 88ab063b64 fix(prune-cache): close the reader-marker check-then-delete window
Both eviction sites checked for a consumer's `.reading-` marker and then,
seconds later — `usage_gb` runs `du -sk` over a multi-GB tree between the
two — unlinked the directory. A consumer that started a clone inside that
gap had its source removed mid-walk, which `cp -al` does not report: a
subtree unlinked before its parent is listed is silently omitted.

Unreachable today, and only by policy: snapshots belong to protected refs
and protected refs never reach the marker check. `cargo-cache` and
`cargo-cache-publish` take that ref list as two independent inputs, so a
workflow listing a publisher in one and not the other arms this with no
code change at all.

Closed structurally, with publish-snapshot.sh's rotation rather than a new
mechanism: the candidate is renamed aside and only then re-examined, so the
scan the unlink rests on happens strictly after the rename. A consumer that
resolved the directory published its marker before that scan and cannot be
missed; one arriving after cannot resolve the path and starts cold, the same
degrade the publisher's swap window already produces. Renaming disturbs no
clone in flight — no entry is unlinked and the inode is unchanged — so a
declined eviction costs a deferred eviction and nothing else. A reprieved
cache is put back under its own name; one whose name a concurrent seed has
retaken is left aside and swept by a later pass once its readers drain,
since nothing else globs a dotted name.

prune-cache-selftest gains three scenarios (21 -> 31 assertions). Scenario
12 is the one that bites: the `du` the pass runs on its candidate publishes
the marker, placing it strictly after the check and strictly before the
unlink. Against check-then-delete, 1-11 pass and 12 fails; breaking only
the second look and leaving the rename fails it too.
2026-08-23 23:09:35 -05:00
claudeandClaude Opus 5 3b2dec6a50 test(cargo-cache): cover the stale-reader-marker sweep and its bound
The staleness path decides whether a publisher may reclaim disk, so getting it
wrong means an abandoned marker pins a snapshot generation forever — the exact
outcome the bound exists to prevent. It was previously covered only by
analogy to prune-cache.sh's .ci-lock-* staleness, which is not the bar.

New publish-snapshot-selftest.sh scenario 8 asserts both directions against
the SAME backdated marker, which is what separates "honours the bound" from
"ignores anything that looks old":

* under CACHE_READ_STALE_SECONDS=86400 a three-hour-old marker is left alone
  and still defers reclamation, exactly as a live reader does;
* under the 7200s default the same marker is swept, reported as swept, and the
  generation it was pinning — plus the one deferred by the first half — is
  reclaimed.

Backdated with `touch -d`, not slept for; the suite stays fast.

Red-proven by mutation rather than against the pre-fix scripts, since the
whole mechanism is new there and "it does not exist yet" proves nothing about
the threshold logic. Mutating live_reader_count's bound test to `true` (never
sweep) fails scenario 8:

    ASSERTION FAILED: the stale marker was not reported as swept

and to `false` (sweep everything, bound ignored) fails scenario 6 instead,
which is the right blast radius — ignoring the bound means unlinking under a
LIVE reader:

    ASSERTION FAILED: the previous generation was unlinked while a reader
    still held it

Also documents the entry-count check's measured cost in the README: on ext4
with a warm cache over 78,554 entries, 44 ms per metadata walk against 3,126 ms
for the `cp -al` it guards — about 2.8%. Not a perf-claiming change; the number
is there so the next reader does not have to wonder.

The reviewer's other nit — scenarios 8/9 of the seed suite exercising
publish-snapshot.sh's interlock — was already covered by the cross-reference
in this file's header, so no move.

Verification: `bash scripts/selftest.sh` — 5 suites, exit 0, 88 assertions
(82 before this commit, 63 at baseline). shellcheck: no new findings.

Refs: daniel/gitdan#11, zemyna#911

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sqh2vscfzisk83VuPVQX9L
2026-08-23 16:52:53 -05:00
claudeandClaude Opus 5 719475831b fix(cargo-cache): scope the safety claim to what the code actually prevents
Follow-up to f57e2a6, addressing the reviewer's sharpest question: is the race
"closed by construction", or merely detected and retried? The honest answer is
"both, on different paths", and the README said only the first half.

* README now states three claims separately instead of collapsing them:
  a publisher rotating a snapshot cannot tear a clone of it (by construction —
  the marker ordering prevents the unlink, and the consumer's verification is
  a redundant second check on that path); every OTHER way the source can
  change mid-clone is detected, not prevented (the eviction pass's reader
  check is check-then-delete, and a seed-fallback-dir has no interlock at all
  — there, verification plus a bounded retry and a loud failure is the whole
  guard); and disk reclamation is bounded rather than immediate. Overclaiming
  this property once was the finding; overclaiming it twice would be worse.

* publish-snapshot-selftest.sh now covers the PUBLISHER's half of the race,
  where a reader of the swap belongs. Scenario 3 only ever covered a consumer
  that had already FINISHED cloning — safe for free, since its own hardlinks
  keep the inodes alive. New scenario 6 covers a reader still in flight past
  the grace period (the generation is left on disk, the deferral is warned
  about, and an earlier consumer is still unaffected); scenario 7 covers the
  sweep, so "we defer instead of forcing" cannot quietly become a disk leak.
  Red-proven against 248af306's scripts:

    ASSERTION FAILED: the previous generation was unlinked while a reader
    still held it

  The consumer's half stays in seed-target-dir-selftest.sh scenario 8, which
  still red-proves at 16693 of 48805 entries against the same scripts.

* seed-target-dir-selftest.sh now asserts what happens when the retries are
  EXHAUSTED, not just what hardlink_clone_into returns: an unreadable source
  makes the seed script exit non-zero, name the reason, leave no target dir,
  and — the one that matters — not fall through to its cold-start branch. A
  corrupt-cache bug degrading into an invisible 4x-slower CI job is the
  failure mode worth pinning down. Skipped when running as root, where mode
  bits deny nothing.

* usage_kb: a directory we cannot read measured as the empty string, which was
  then spliced into usage_gb's awk program and made it a syntax error at the
  exact moment something was already going wrong. Now measures 0.

Verification: `bash scripts/selftest.sh` — 5 suites, exit 0, 82 assertions
(was 75 after f57e2a6, 63 before). shellcheck over scripts/: no new findings.

Measured the cost the reviewer asked about, on ext4, warm cache, 78,554
entries: `cp -al` 3126 ms against 44 ms for one `find | wc -l`. Two counts per
attempt is ~2.8% on top of the clone. Not measured on the CI runner's volume.

Refs: daniel/gitdan#11, zemyna#911

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sqh2vscfzisk83VuPVQX9L
2026-08-23 16:49:44 -05:00
claudeandClaude Opus 5 f57e2a6013 fix(cargo-cache): close the seed-vs-republish race the design claimed to close
The shared action's justification over zemyna's and emowheel's schemes was
that hardlink-cloning from a published snapshot closes gitdan #911 "by
construction, not by the single job slot". Review disproved that. This makes
the claim true, and corrects the README where it could only be bounded.

Finding 1 (verdict-level) — silent partial clone
------------------------------------------------
`hardlink_clone_into` ran `cp -al` with no exit-status check, and both call
sites invoked it as a condition, which suppresses `set -e` for the whole call.
A publisher's `rm -rf` of the generation it rotated away therefore unlinked
entries beneath an in-flight consumer walk, and the truncated tree was renamed
into place and reported as success.

Both layers are fixed:

* The consumer verifies its own clone. Every attempt checks `cp -al`'s status
  explicitly, the source directory's inode before and after (a wholesale
  replacement mid-walk splices two generations), and the entry count — the
  only signal for a subtree unlinked before its parent was listed, since
  `cp -al` reports no error for one it never saw. Any failure discards the
  staging tree and retries; exhausting the attempts returns a distinct status
  2 and fails the job rather than seeding a partial cache. `unshare_subtree` /
  `_unshare_files` now propagate failure too — a swallowed unshare leaves the
  clone aliasing its source, the exact corruption that step exists to prevent.
* The publisher does not unlink under a reader. A consumer publishes a
  `.reading-<snapshot>-<tag>` marker before it resolves the snapshot path; the
  publisher scans for markers after its first rename. A consumer holding the
  old generation therefore published its marker before that scan and cannot be
  missed; one arriving after the scan necessarily resolves to the new
  generation. The publisher waits for readers to drain and, on timeout,
  DEFERS reclamation rather than forcing it — the old generation is left as
  `.publish-old-<key>-<tag>` and swept by a later publish.

So correctness is closed by construction; disk reclamation is bounded, not
immediate. The residual is capped at one deferred generation per publisher
ref, and the README now says exactly that instead of the disproved claim.

Finding 2 — restore-mtimes.sh ran with no errexit
-------------------------------------------------
`set -euo pipefail` was glued to the end of a comment (`# soundness.set -euo
pipefail`), so it was entirely commented out: a partial failure of the
`git log | awk` pipeline would have produced wrong mtimes across the whole
restore instead of failing loudly. Moved to its own line. Audited every other
script for the same defect — this was the only instance. Independent
confirmation: shellcheck's two SC2164 warnings on this file's `cd "$repo_root"`
disappear now that errexit is actually in effect.

Finding 3 — lock-acquire window
-------------------------------
A just-seeded directory was unlocked until a later action step, so a
concurrent job's prune pass could evict it. `seed-target-dir.sh` now takes an
optional lock-id and writes the lock marker on every path out of the script,
including into the staging tree before its rename, so the directory carries a
lock the instant it appears under its final name. The action's acquire step
stays (it is idempotent and stamps the LRU marker).

Also hardened `prune-cache.sh` to treat a directory with live reader markers
as locked. Today no reachable configuration prunes a snapshot — only protected
refs publish them and protected refs are excluded from every pass — so this is
redundant by policy; it is here so that stops being the reason it is safe.

Verification
------------
New selftest scenario 8 races a real seed against a real publish rotation,
gating the rotation on the seed's *observed* clone progress so the window is
hit deterministically rather than on a fast machine's coin flip. Red-proven
against the unguarded scripts, three consecutive runs:

  ASSERTION FAILED: the seeded tree is truncated: 15443 entries against the
  snapshot's 493 (was 48805 before the rotation)      (15443 / 16986 / 16498)

Green after the fix, six consecutive runs, catching the clone mid-walk at
~10.5k of 48805 entries each time. Scenario 9 covers deferred reclamation and
its later sweep; scenario 10 covers an unreadable source failing loudly.

`bash scripts/selftest.sh`: 5 suites, exit 0, 75 assertions (was 63).
shellcheck over `scripts/`: no new findings, two SC2164 warnings resolved.

Docs: README's republish-safety paragraph replaced with what the code now
guarantees, including the bounded disk residual stated explicitly; new
`read-grace-seconds` / `reader-stale-seconds` inputs documented in the
`cargo-cache-publish` table; the selftest table names the new race.

Refs: daniel/gitdan#11, zemyna#911

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sqh2vscfzisk83VuPVQX9L
2026-08-23 16:40:21 -05:00
claudeandClaude Opus 5 248af3061e feat(cargo-cache): hardlink-clone a per-ref Cargo cache from a published snapshot
Replaces the phase-0 resolution probe with the real actions, merging the two
independent per-branch Cargo cache implementations on this forge into the
design neither of them had.

## The merge

- zemyna seeds a PR branch by `cp -al` hardlink clone (near-free: cost scales
  with inode count, not bytes) from the base branch's LIVE target dir — a
  torn read waiting for a second job slot (its own #911).
- emowheel seeds from a PUBLISHED IMMUTABLE SNAPSHOT (no race by
  construction) but with `cp -a`, duplicating ~35 GB per branch.

This ships hardlink-clone FROM a published snapshot: zemyna's cost profile,
emowheel's soundness, and #911 closed structurally rather than by the runner
happening to have one execution slot.

## The bug both implementations have

A build inside a `cp -al` clone DOES mutate the directory it was cloned from.
Cargo replaces real artifacts, but writes its metadata — and build scripts
write their OUT_DIR — with a plain truncating write, straight through the
shared inode. Measured set: `.fingerprint/<unit>/dep-<target>` (under
CARGO_UNSTABLE_CHECKSUM_FRESHNESS), `build/<pkg>/{output,root-output,out/**}`,
`deps/*.d` and `<profile>/*.d`.

The checksum-freshness case is a wrong answer, not a slow build: a PR clone
rewrites the base's dep-info to describe the PR's sources while the base's
cache still holds the artifact built from the base's; once the PR merges, the
base's next run finds the checksums match, reports `Fresh`, and links a binary
built from the pre-merge code. Reproduced end to end.

Fix: hardlink the artifacts (the GB), real-copy the metadata (the MB) — about
3.7% of a 6.9 GB Bevy target dir, against 100% for a full copy.

## Contents

- `cargo-cache/action.yml` — consume: resolve keys, seed from the base's
  snapshot via staging + one atomic rename, strip Cargo lock files, unshare
  the mutable paths, restore mtimes from git history, lock, prune.
- `cargo-cache-publish/action.yml` — publish: record the build watermark,
  atomically republish the snapshot on a protected branch, release the lock
  (`mode: release-lock` for the `if: always()` step).
- `scripts/` — all logic, so it is testable standalone; the YAML is wiring.
- `scripts/*selftest.sh` + `selftest.sh` — five suites, 63 assertions, every
  fix paired with a control that reproduces the bug. All green locally.

Eviction merges emowheel's liveness pass (dead branches pruned
unconditionally, not gated on disk pressure) with LRU-under-pressure, but
inverts the order within the pressure pass: `target-*` before `snapshot-*`,
because a snapshot is hardlinked to everything cloned from it, so evicting one
frees almost no real bytes while costing every future PR its warm start.

restore-mtimes.sh is ported from emowheel (the watermark variant, which closes
the merge hazard zemyna's copy still has) with its provenance de-projectised.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sqh2vscfzisk83VuPVQX9L
2026-08-23 14:18:01 -05:00
claude 8503883138 feat: cargo-cache composite action skeleton (phase-0 resolution probe) 2026-08-23 11:52:31 -05:00