fix: resolve the git repository from cwd instead of the inherited environment - #2255

Fixes #2027

The environment variable alone reproduces it, no hook or worktree needed:

npx changeset status --since=origin/main                                       # works
GIT_DIR=$(git rev-parse --git-dir) npx changeset status --since=origin/main    # fails

Git runs hooks with GIT_DIR pointing at the worktree-specific git directory and does not set GIT_WORK_TREE (an ordinary checkout gets neither, which is why only worktree pushes are affected). With GIT_DIR set and GIT_WORK_TREE unset, git treats cwd itself as the work tree root. Calls in @changesets/git pass cwd but inherit the environment, so the inherited GIT_DIR wins. filterChangesetsSinceRef passes cwd as the .changeset directory, so git diff --name-only --diff-filter=d looks for each committed path under .changeset/<path>, finds nothing, classifies every file as deleted, and filters them all out.

The fix

The exec wrapper strips the inherited variables that would redirect git away from the repository containing cwd. Routing every call through one helper covers the other git-shelling commands, not just the one in the report. tinyexec merges with process.env, so variables are dropped by overriding with undefined; keys match case-insensitively for Windows.

Only GIT_DIR is needed for this bug. I included the rest of the repository/work-tree/object-store/index set because leaving them keeps the same failure alive for a pre-commit hook that sets GIT_INDEX_FILE. Happy to narrow. packages/release-utils/src/gitUtils.ts spawns git the same way and I left it alone, since it runs in the action on an ordinary checkout where neither variable is set.

Alternatives rejected

Setting GIT_WORK_TREE alongside the inherited GIT_DIR, as the issue suggests, is circular: finding the correct value needs the real worktree root, and asking git for it needs an already-correct environment. Setting it to cwd is wrong in exactly the failing case.

Honouring the pair when a caller sets both is not coherent: @manypkg/get-packages reads package.json from cwd regardless, so a GIT_WORK_TREE pointing elsewhere means git and the filesystem disagree about which project is being inspected.

Fixing it locally in @changesets/read would leave the wrapper sensitive to GIT_INDEX_FILE, and any future caller passing a subdirectory would reintroduce it.

Testing

Three tests in packages/git/src/index.test.ts, all red on main: getCurrentCommitId reporting the cwd repository's HEAD rather than the one GIT_DIR points at, and getChangedChangesetFilesSinceRef finding the changeset both with cwd at .changeset and in a real git worktree add worktree.

End to end, a real pre-push hook running changeset status --since=origin/main from a worktree rejects the push on main and succeeds here, same commit and hook. pnpm types:check, pnpm lint, pnpm format clean; git, read and status suites pass. The pack/publish e2e snapshot tests fail for me, but identically on main with the same counts, so that is my local package manager versions. Changeset included.