Resolve repository hooks from the common directory

[YuriNachos]

Fixes #1053

Summary

pre-commit, pre-push, and other Git hooks are now found when the repository is a linked worktree. Previously GitUp silently skipped hooks for worktrees because it looked them up in the wrong directory.

Root Cause

-pathForHookWithName: built the default hooks directory from self.repositoryPath, i.e. git_repository_path(). For a linked worktree that returns the per-worktree git directory (e.g. <main>/.git/worktrees/<name>), which never contains a hooks directory. Git stores hooks in the repository common directory (<main>/.git/hooks), shared by all linked worktrees, so GitUp never found them and runHookWithName: (used for the pre-push hook in -sendLocalBranchesToRemote:...) silently treated them as absent.

Changes

• GitUpKit/Core/GCRepository.m
  • In -pathForHookWithName:, derive the default hooks path from git_repository_commondir(_private) instead of self.repositoryPath. For a plain repository the common directory equals the git directory, so behavior is unchanged; only linked worktrees are affected.

Test plan

• Added testPathForHookWithName_FoundFromLinkedWorktree to GCRepository-Tests.m (GCMultipleCommitsRepositoryTests): creates a linked worktree via git worktree add, installs an executable pre-commit hook in the main repository hooks directory, and asserts the worktree resolves the hook to that shared path.
• Verified red→green locally:

  cd GitUpKit
  xcodebuild test -scheme "GitUpKit (macOS)" -destination "platform=macOS" \
    -only-testing:Tests/GCMultipleCommitsRepositoryTests/testPathForHookWithName_FoundFromLinkedWorktree \
    CODE_SIGN_IDENTITY="" CODE_SIGNING_REQUIRED=NO CODE_SIGNING_ALLOWED=NO
  

  The new test fails on master (worktree cannot resolve the hook) and passes with this change.
• Existing testPathForHookWithName, testPathForHookWithName_AbsoluteCustomHooksPath, and testPathForHookWithName_RelativeCustomHooksPath are unaffected (a plain repo has commondir == gitdir, and the custom core.hooksPath branch is untouched).

I AGREE TO THE GITUP CONTRIBUTOR LICENSE AGREEMENT

[greptile-apps]

Greptile Summary

The PR corrects default Git hook discovery for linked worktrees by resolving hooks relative to libgit2’s shared repository common directory.

• Uses git_repository_commondir while leaving custom core.hooksPath handling unchanged.
• Adds a regression test that creates a linked worktree and verifies discovery of a shared executable hook.

Confidence Score: 5/5

The PR appears safe to merge, with no actionable correctness or security issues identified.

The common-directory API supplies the correct hook base for linked worktrees while preserving plain and bare repository behavior, and the regression test directly covers the corrected path.

Important Files Changed

Filename	Overview
GitUpKit/Core/GCRepository.m	Correctly changes default hook resolution from the per-worktree Git directory to the shared common directory.
GitUpKit/Core/GCRepository-Tests.m	Adds focused linked-worktree coverage that exercises the previous failure and verifies the resolved shared hook path.

_{Reviews (1): Last reviewed commit: "Resolve repository hooks from the common..." | Re-trigger Greptile}