Prevent checkout under an external index lock - #15641
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krlvi
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Pull request overview
This PR adds an early “index lock” preflight to but_core::worktree::safe_checkout_from_head() so a checkout fails immediately if the worktree’s index is already externally locked, preventing libgit2 from partially mutating the worktree before reporting the error. It also adds regression tests covering repository-state preservation and correct index-path handling for linked worktrees.
Changes:
- Add a preflight probe for the worktree’s index lock before invoking libgit2 checkout logic.
- Add tests ensuring an external index lock prevents any checkout side effects (worktree/index/HEAD/ref) and that linked worktrees use their own index path.
- Wire the new test module into the existing worktree test suite.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
crates/but-core/src/worktree/checkout/function.rs |
Adds an early index-lock acquisition attempt to fail before libgit2 performs any worktree mutations. |
crates/but-core/tests/core/worktree/mod.rs |
Registers the new checkout_index_lock test module. |
crates/but-core/tests/core/worktree/checkout_index_lock.rs |
New regression tests for index-lock preflight behavior and linked-worktree index paths. |
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Reviewed commit: 569a4873d9
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Context
Trigger: run safe checkout while the repository index is already locked by another process.
Symptom: checkout can change worktree files before returning the index-lock error, leaving a failed operation partially applied.
Change
Probe the exact worktree index lock before checkout starts. A lock held at the probe now fails before worktree, index, HEAD, or ref mutation; uncontended checkout behavior stays on the existing libgit2 path. This is a fail-fast preflight, not full checkout serialization: contention beginning after the probe remains outside this bounded change. Regression coverage includes repository-state preservation and linked-worktree index paths.
Related: #5390