Fix git worktree popup popup no worktree when opened in a project (#55053) (cherry-pick to preview)

[zed-zippy]

Cherry-pick of #55053 to preview

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Summary

Fixes the git: worktree popup showing no worktrees when a project is
opened at the parent of a .bare directory (the common
bare-clone-with-sibling-worktrees layout).

What's fixed

• crates/git/src/repository.rs

• New git_binary_for_worktree_list helper that uses
  repository.path() as the working directory when workdir() is None.

  • worktrees() switched to the new helper.

• parse_worktrees_from_str accepts bare entries without a HEAD line.

• Tests

• Unit test: parser handles a bare entry with no HEAD followed by a
  normal worktree entry.

• Integration test: full .git-file → .bare + sibling worktrees
  layout (main, feature-a, feature-b) is listed correctly via the
  real git binary.

UI rendering already gates on empty sha (worktree_picker.rs uses
.when(!sha.is_empty(), ...)), so the bare entry's empty sha renders
without artifacts.

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments — N/A, no unsafe
• The content is consistent with the UI/UX
  checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable — same
  single git worktree list --porcelain invocation, no extra work

Closes #54824

Video

Screencast.from.2026-04-28.09-43-45.webm

Release Notes:

• Fixed the git: worktree popup listing no worktrees when a project
  was opened at the parent of a .bare directory
  (bare-clone-with-sibling-worktrees layout).

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Co-authored-by: Max Brunsfeld maxbrunsfeld@gmail.com