rebase

name	rebase
description	Rebase the current branch.
allowed-tools	Bash
disable-model-invocation	true

Rebase the current branch.

Arguments: $ARGUMENTS

Behavior:

• No arguments: rebase on local main
• "origin": fetch origin, rebase on origin/main
• "origin/branch": fetch origin, rebase on origin/branch
• "branch": rebase on local branch

Steps:

1. Check for uncommitted changes:
   • Run git status --porcelain
   • If there are changes, run git stash push -m "rebase-temp"
   • Remember to pop the stash after rebase completes
2. Parse arguments:
   • No args → target is "main", no fetch
   • Contains "/" (e.g., "origin/develop") → split into remote and branch, fetch remote, target is remote/branch
   • Just "origin" → fetch origin, target is "origin/main"
   • Anything else → target is that branch name, no fetch
3. If fetching, run: git fetch <remote>
4. Detect already-merged commits (see below)
5. Run: git rebase <target> (or git rebase --onto if stale commits found)
6. If conflicts occur, handle them carefully (see below)
7. Continue until rebase is complete
8. If workmux-base was used and pointed to a merged branch, update it to the target branch (strip remote prefix for the config value):

   git config branch.<branch>.workmux-base main
   

9. If changes were stashed in step 1, run git stash pop

Detecting already-merged base branches:

When a branch was based on another branch that was squash-merged into the target, the old commits still appear in the branch history but their changes are already in the target. A plain git rebase will try to replay them all, causing repeated conflicts that need to be skipped one by one.

Before rebasing, detect this situation and use --onto to skip stale commits:

1. Check if workmux stored a base branch for the current branch:

   base=$(git config --get branch.$(git branch --show-current).workmux-base)
   

2. If a base branch is found and it's NOT the rebase target (e.g. base is analytics-app-detail but we're rebasing onto origin/main):
   • Check if the base branch has been merged into the target:

     git merge-base --is-ancestor <base> <target>
     

   • If it HAS been merged (exit code 0), find where our branch diverged from the base branch:

     fork_point=$(git merge-base <base> HEAD)
     

   • Then find the last commit on our branch that was part of the base branch (i.e. the last commit before our own work started):

     # The tip of the old base branch in our history
     last_stale=$(git rev-list --ancestry-path $fork_point..HEAD \
       --not <target> | tail -1)^
     

     Or more simply: the merge-base between the base branch tip and HEAD gives the fork point, and all commits between that and the first commit unique to our branch are stale. Use:

     git rebase --onto <target> <base> HEAD
     

     This replays only commits after the base branch tip onto the target.
   • If the base branch has NOT been merged, fall through to a normal rebase.
3. If no workmux base is found, fall back to heuristic detection: walk commits oldest-to-newest and check if each commit's file changes already match the target using git diff --quiet. Find the last stale commit and use git rebase --onto <target> <last-stale-commit>.
4. If no stale commits are detected by either method, use a plain git rebase <target>.

Handling conflicts:

• BEFORE resolving any conflict, understand what changes were made to each conflicting file in the target branch
• For each conflicting file, run git log -p -n 3 <target> -- <file> to see recent changes to that file in the target branch
• The goal is to preserve BOTH the changes from the target branch AND our branch's changes
• After resolving each conflict, stage the file and continue with git rebase --continue
• If a conflict is too complex or unclear, ask for guidance before proceeding