drn/rebase

Context

• Current branch: !git branch --show-current
• Git status: !git status --short
• Remotes: !git remote -v 2>/dev/null | head -10
• HEAD ref: !git rev-parse --abbrev-ref HEAD 2>/dev/null | head -1
• Open PR: !gh pr view --json number,url,headRefName 2>/dev/null | head -10
• Base ref: !git branch -r 2>/dev/null | grep -oE 'origin/(main|master)' | head -1
• Commits vs main: !git log origin/main..HEAD --oneline 2>/dev/null | head -20
• Commits vs master: !git log origin/master..HEAD --oneline 2>/dev/null | head -20
• Arguments: $ARGUMENTS

Your task

Rebase the current branch onto the latest upstream default branch and force-push to update the remote PR branch.

Step 0: Validate state

• If HEAD is detached (not on a named branch), stop and tell the user: "Cannot rebase in detached HEAD state."
• Determine the current branch name.

Step 1: Determine the target remote

• Run git remote to list remotes.
• If upstream exists, use upstream as the target remote.
• Otherwise, use origin.

Step 2: Determine the default branch

If the user passed --onto <branch> in the arguments, use that branch as the rebase target instead of the default branch. Otherwise:

• Run git symbolic-ref refs/remotes/<remote>/HEAD 2>/dev/null (where remote is from Step 1) and extract the branch name.
• If that fails, check if <remote>/main exists with git rev-parse --verify <remote>/main 2>/dev/null.
• If that fails, check if <remote>/master exists with git rev-parse --verify <remote>/master 2>/dev/null.
• If none work, stop and tell the user: "Could not determine the default branch. Use --onto <branch> to specify."

If the current branch IS the default branch, stop and tell the user: "You are on the default branch. Rebase is not needed."

Step 3: Fetch

• Run git fetch <remote> <default-branch>.
• Report: "Fetching <remote>/<default-branch>..."

Step 4: Check if rebase is needed

• Run git merge-base --is-ancestor <remote>/<default-branch> HEAD to check if already up to date.
• If the branch is already up to date (exit code 0 from the above), report "Already up to date with <remote>/<default-branch>." and skip to Step 6.

Step 5: Rebase

• Count the commits to be rebased: git log <remote>/<default-branch>..HEAD --oneline
• Report: "Rebasing N commits onto <remote>/<default-branch>..."
• Run git rebase <remote>/<default-branch>.
• If conflicts arise:
  • Show the user which files have conflicts (use git diff --name-only --diff-filter=U).
  • Resolve each conflict. Read the conflicting files, understand both sides, and make the correct resolution.
  • After resolving each file, run git add <file>.
  • Run git rebase --continue.
  • If further conflicts arise, repeat the process.
  • Report each conflict and how it was resolved.
  • If a conflict cannot be resolved confidently, run git rebase --abort, report the issue, and stop. Do not guess at resolutions that could lose work.
• Report: "Rebased successfully."

Step 6: Force push (conditional)

• Check if the current branch has a remote tracking branch by running git rev-parse --abbrev-ref @{upstream} 2>/dev/null.
• Use mcp__github__list_pull_requests (with head set to <owner>:<branch>, state: "open") to check if there is an open PR.
• If there is an open PR:
  • Run git push --force-with-lease to update the PR branch.
  • Report: "Force pushed to origin/<branch> (open PR #N)."
• If there is no open PR but there IS a remote tracking branch:
  • Run git push --force-with-lease to update the remote branch.
  • Report: "Force pushed to origin/<branch> (no open PR)."
• If there is no remote tracking branch:
  • Skip the push.
  • Report: "No remote tracking branch. Skipped push."
• If the MCP GitHub tools are not available, skip the PR check, and only push if there is a remote tracking branch.

Step 7: Report summary

Print a concise summary of what happened:

• How many commits were rebased (or "already up to date")
• Whether conflicts were resolved and in which files
• Whether the branch was pushed and to where
• The PR URL if one exists