Git Branch Cleanup

Prune locals = merged OR remote gone. Destructive -> preview + confirm.

Flow

0. If user mentioned keep-patterns inline (e.g. "but keep spike/*") -> capture them. Else assume none. Don't prompt up front
1. Parallel:
   • git fetch --all --prune
   • git branch --show-current
2. Base: user names one -> use it. Else detect: git symbolic-ref --short refs/remotes/origin/HEAD -> strip the origin/; ref missing -> git remote set-head origin -a, re-read; no remote -> main, fall back master. Why -> this is a delete path, and --merged <wrong-base> misclassifies live branches as merged. Compare against origin/<base>, not the local ref -> the local base is often stale or absent entirely (git-branch-create branches off origin/<base> without ever creating it), so a local-ref check either errors or reports branches as unmerged that the remote already has
3. Candidates:
   • Gone: upstream gone

     git for-each-ref --format='%(refname:short) %(upstream:track)' refs/heads \
       | awk '$2 == "[gone]" {print $1}'

   • Merged: fully merged into the remote base (step 1 already fetched + pruned)

     git branch --merged origin/<base> --format='%(refname:short)'

   • No remote -> compare against the local <base> (git branch --merged <base>) and skip the Gone bucket entirely (no upstreams can exist)
   • Note: squash-merged PRs leave no merge commit, so they won't appear in Merged. Closing the PR deletes the remote -> they show up in Gone instead. The Gone bucket is the catch-all for PR-merged work
   • Union. Exclude:
     • Current
     • Base (main/master)
     • Protected: exact names develop, staging, plus any branch matching the glob release/*. Skip silently if none exist
     • User keep-patterns from step 0 (if provided)
4. Print grouped by reason (gone vs merged), one line per branch, no prose. Ask confirm
5. On confirm:
   • Merged: git branch -d <name>. -d re-checks against HEAD/upstream, not origin/<base>, so it can refuse a branch the Merged bucket listed -> that's a safe refusal, not a bug: report it as skipped, don't reach for -D
   • Gone + unmerged: git branch -D <name>. Explicit confirm only
   • Branch checked out in another worktree -> both -d and -D refuse. Same safe refusal: report as skipped, don't force it
6. Print summary: counts + one line per skipped branch (+ why). No recap of what was already listed

Rules

• Always preview + confirm. Skip prompt only if user already said "yes delete" / "go ahead" same turn - covers -d only; -D of unmerged work always gets its own named-branch confirm
• Never delete current / base / HEAD
• Never -D unmerged without explicit OK. Unsure -> list + let user decide
• Never touch remote branches. Local only
• Never git reflog expire / gc --prune=now. Deleted stay recoverable via reflog
• Empty candidate list -> say so + stop
• User keep-patterns (wip/*, spike/*) -> off-limits