fix: resilient worktree removal on Windows file-lock (#302)

[getappz]

Summary

Supersedes #306, which is stuck in a CONFLICTING state — its branch (feat/worktree-audit-294) still carries the pre-squash commit history of the already-merged #294/#304, diverging from master's squashed version at the git-object level (no actual content conflict, just incompatible history). Rebuilding cleanly on current master instead of fighting that.

Cherry-picked the one genuinely new commit from that branch and fixed two gaps found in review:

• fmt: one eprintln! wasn't rustfmt-clean — CI's fmt job would have failed had it run (it never did on fix: resilient worktree removal on Windows file-lock (#302) #306, blocked by the CONFLICTING status; only CLA/CodeQL/CodeRabbit reported).
• Tests: the new remove_worktree_dir (retry + backoff, cmd /c rmdir fallback, handle64.exe/handle.exe locking-process detection) had zero test coverage. Added two: a happy-path removal, and a genuine lock-then-release test (opens a file handle, drops it from a background thread after 250ms, asserts the retry loop succeeds within budget) — meaningful on Windows where an open handle actually blocks remove_dir_all; harmless no-op assertion on Unix where it doesn't.

Changes (from item #302)

• remove_worktree_dir() in gc_orphans: retry remove_dir_all with exponential backoff (100ms-1.6s, ~3.1s total + one final attempt), fall back to cmd /c rmdir /s /q on Windows, then try handle64.exe/handle.exe (Sysinternals, if present — fails gracefully via Command's Err path if not installed) to report the locking process.
• cleanup-branches.sh: retry git worktree remove up to 5x with backoff, distinguish a genuine lock (Permission denied) from dirty/uncommitted (never retried, still skipped immediately), warn and fall through on a persistent lock instead of blocking the rest of the cleanup run.

Test plan

• cargo test -p flare-git-core — 98/98 pass (2 new)
• cargo fmt --all -- --check — clean
• cargo clippy -p flare-git-core --all-targets --all-features -- -D warnings -A unsafe_code -A clippy::pedantic — clean
• bash -n scripts/cleanup-branches.sh — syntax valid (shellcheck not available in this environment)

Note for reviewers

cmd /c rmdir receives the worktree path as a Command::args() element (not shell-concatenated), but cmd.exe itself still parses %...%/&/| inside whatever it receives. Not fixed here — worktree paths in this codebase are always internally constructed from repo_root + a numeric sequence_id/branch-derived name, never external/untrusted input, so real-world exploitability is effectively nil. Flagging for the record rather than adding defensive escaping for a threat model that doesn't apply.

[coderabbitai]

Warning

Review limit reached

@getappz, you've reached your PR review limit, so we couldn't start this review.

Next review available in: 51 minutes

Enable usage-based reviews in Billing to review now. Otherwise, wait until the next included review is available.
You're only billed for reviews past your plan's rate limits ($0.25/file).

How can I continue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

To avoid repeated limits, reduce automatic review volume by pausing incremental auto-reviews earlier, using label-based review opt-in, excluding WIP or generated PR titles, or requesting reviews manually when the PR is ready. If your team needs uninterrupted high-volume reviews, an organization admin can enable usage-based reviews.

How do review limits work?

CodeRabbit enforces per-developer PR review limits for each organization. Most developers receive the normal plan review availability.

For paid Pro and Pro+ PR reviews, CodeRabbit uses adaptive limits for sustained high-volume activity. When a developer's recent PR review activity reaches the 95th percentile or higher among CodeRabbit users, additional reviews become available more gradually as earlier reviews age out of the rolling window.

Please refer docs for additional details.

Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 20797eaa-850e-4822-9df1-0fed832e5759

📥 Commits

Reviewing files that changed from the base of the PR and between 921b472 and 888be54.

📒 Files selected for processing (2)

• crates/flare-git-core/src/worktree.rs
• scripts/cleanup-branches.sh

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch task/308

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}