fix(betterer 🐛): don't reinitialize an existing git repo (corrupts shared config in worktrees)

[mattmorganpdx]

What

BettererGitΩ._init() ran git init on every Betterer run. This PR skips it when we're already inside a git repository, and fixes the retry loop so init errors are actually surfaced.

Why

init() calls _findGitRoot() first, which throws unless a .git already exists — so by the time _init() runs, the repository is guaranteed to be initialized and the git init is redundant.

It's also harmful in git worktree setups. When Betterer runs inside a linked worktree (<worktree>/.git is a gitfile pointing into a shared common git dir), the redundant git init reinitializes against the common git dir and rewrites shared config — flipping core.bare and breaking every worktree on the repo.

This is reliably reproducible with the popular "bare clone + worktree" layout:

git clone --bare <url> repo.git        # core.bare = true
git -C repo.git worktree add ../wt main
# core.bare is still true here...
git -C ../wt init                      # Reinitialized existing Git repository
# core.bare in repo.git/config is now FALSE — every worktree is broken

Separately, the retry loop could never rethrow:

for (let i = 0; i < retries; i++) {
  try { await git.init(); }
  catch (error) { if (i >= retries) throw error; }  // i maxes at retries-1, so never true
}

so any git init failure (e.g. parallel workers colliding on the config lock — error: could not lock config file …/config: File exists) was silently swallowed.

Changes

• packages/betterer/src/fs/git.ts: guard git.init() behind git.checkIsRepo() so an already-initialized repo is never reinitialized; fix the retry condition (i === retries - 1) and return on success.

private async _init(git: SimpleGit): Promise<void> {
  if (await git.checkIsRepo()) {
    return;
  }

  const retries = 3;
  for (let i = 0; i < retries; i++) {
    try {
      await git.init();
      return;
    } catch (error) {
      if (i === retries - 1) {
        throw error;
      }
    }
  }
}

• test/worktree.spec.ts: new regression test that builds a bare-repo + linked-worktree layout, runs Betterer inside the worktree, and asserts the shared common-dir core.bare is untouched. It fails against the current code (core.bare flips true → false) and passes with this change.

Behavior impact

• Normal (already-initialized) repos: git init is no longer invoked — previously a no-op, now skipped entirely. No functional change to Betterer's results.
• Worktree / shared-common-dir repos: the shared config is no longer mutated, so core.bare can't be flipped.
• Genuinely uninitialized directory: unchanged — init() still runs (and now correctly throws after exhausting retries instead of swallowing the error). Note that _findGitRoot() already throws before reaching here unless a .git exists, so this path is effectively unreachable today; the guard is defensive and self-documenting.

Note on v6

This targets the master (5.x) line, where the bug lives. The v6/nx rewrite already removed this code path — BettererGitΩ no longer calls git init and version control is only created in precommit mode — so there's nothing to port forward. This is purely a 5.x fix.

Possibly related: #1129 (same _findGitRoot/init area).

[phenomnomnominal]

I think the code is self explanatory here, would you mind removing the comments?

[phenomnomnominal]

Thanks, oops 😅

[phenomnomnominal]

the fixture should have utilities for making paths and writing files etc, which the cleanup will then handle.

[phenomnomnominal]

Not a huge fan of the direct git calls, is it possible to do this with simple-git which should be available? I understand it's more complex git behaviour so it might just be necessary.

[phenomnomnominal]

Don't think the comments here are necessary either.

[phenomnomnominal]

The E2E tests failing is "normal" ftr

[mattmorganpdx]

Thanks for the quick review! Addressed in 2269888:

• Removed the comments from _init and the test.
• Test now uses the createFixture utilities for paths/files (cleanup handles teardown) instead of manual fs calls.
• Switched the git setup to simple-git — .init/.addConfig/.add/.commit/.revparse/.clone, with .raw(...) only for worktree add and reading core.bare since those don't have dedicated methods.

Re-verified it fails against the original _init and passes with the fix.