tests/test_lane_worktrees.py: test_yes_is_refused_for_a_lane_live_elsewhere_or_unread flakes when git packs projects/repoA's objects between its two snapshots #231

What failed

tests/test_lane_worktrees.py::test_yes_is_refused_for_a_lane_live_elsewhere_or_unread[none-binding1-could not be read]

This failed in CI run 38465762981, attempt 1, Linux tests job (head fab2cbc, PR #214, git 2.55.0 on the runner): https://github.com/opensoft/openRepoTools/actions/runs/38465762981/job/115532049111. The job ended 1 failed, 1429 passed, 9 skipped in 3065.66s.

Attempt 2 of the same run passed, with no code change: 1430 passed, 9 skipped in 2482.85s, https://github.com/opensoft/openRepoTools/actions/runs/38465762981/job/117498706925.

The failing assertion is the case's "a refused --yes changes nothing" check (tests/test_lane_worktrees.py:636):

>       assert snapshot(estate.root, skip=skip) == before
E       AssertionError: assert {'config': (1...d411d4'), ...} == {'config': (1...d411d4'), ...}
E         Omitting 150 identical items, use -vv to show
E         Left contains 6 more items:
E         {'projects/repoA/.git/info/refs': …,
E          'projects/repoA/.git/objects/info/packs': …,
E          'projects/repoA/.git/objects/pack/multi-pack-index': …,
E          'projects/repoA/.git/objects/pack/pack-b73630ba….idx': …,
E          'projects/repoA/.git/objects/pack/pack-b73630ba….pack': …,
E          'projects/repoA/.git/objects/pack/pack-b73630ba….rev': …}
E         Right contains 17 more items:
E         {'projects/repoA/.git/objects/17': …,
E          'projects/repoA/.git/objects/17/b8037e56…': …,
E          'projects/repoA/.git/objects/1f/096e9c…': …,
E          'projects/repoA/.git/objects/bitmap-ref-tips_bnYr5X': …,
E          'projects/repoA/.git/objects/cf/f5543…': …, …}

Analysis

The test races git's own object packing. Nothing in the case wrote those files.

• snapshot() (tests/test_lane_worktrees.py:350) hashes every path under the estate, including each repository's .git/objects. So it compares object STORAGE LAYOUT, not repository content.
• Between the before snapshot and the one after the refused --yes, git consolidated projects/repoA's loose objects into a pack. The before side has loose objects and a bitmap-ref-tips_* temp file. The after side has a pack, a multi-pack-index, and the info/refs and objects/info/packs that update-server-info writes. That is the signature of an automatic git repack (--write-midx with bitmaps), not of anything lane-worktrees does. Its source has no repack, gc or maintenance call, only a git fetch --prune on a probe (lane-worktrees:2394).
• The fixture isolates system config (GIT_CONFIG_NOSYSTEM=1, :161) but not gc or maintenance. git's automatic maintenance runs after commands such as commit and fetch, and by default it DETACHES and finishes in the background. So a repack started by the test's own estate.commit(…), or by a command the sweep runs, can land at any moment. I did not identify which command started it. It passed on re-run, so it is timing, not logic.
• The fake lanes-edit.sh is not involved. This case's Estate fixture puts a Python stub on PATH and points LANES_EDIT at it (:141, :157).

Suggested fix (either is enough; both is belt and braces)

1. Isolate the fixture's repositories from automatic maintenance, as it already isolates system config. In the Estate environment, set GIT_CONFIG_COUNT/GIT_CONFIG_KEY_n/GIT_CONFIG_VALUE_n for gc.auto=0, maintenance.auto=false and gc.autoDetach=false, or point GIT_CONFIG_GLOBAL at a sandbox file carrying them. Then no repack can start, detached or not.
2. Compare content, not layout. Have snapshot() skip .git/objects/**, .git/info/refs and .git/objects/info/packs, and compare each repository's object SET instead (git cat-file --batch-all-objects --batch-check) together with its refs. A repack then changes nothing the test cares about, while a real write still fails it.

The other snapshot(...) == before cases in this file (:568, :753, :816) have the same exposure.

Not related to #214

PR #214 (lanes-edit.sh commit_push) touches neither lane-worktrees nor tests/test_lane_worktrees.py, and this case never runs the real lanes-edit.sh.

Found by lane openRepoTools-4 while working on #214. Not claimed.

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