Skill: sync-stale-branches

Bring old/diverged remote branches up to date with develop. Run this periodically to keep the branch list clean and PR-able.

Inputs

• EXCLUDE — branches to leave untouched (space-separated, no origin/ prefix)
  Default: develop master

Step 1 — List candidate branches

git fetch --prune

# All remote branches minus the exclude list
git branch -r | grep -v 'origin/HEAD' \
  | sed 's|remotes/||' \
  | grep -v -E '^origin/(develop|master)$'

Add any other branches to exclude to the grep pattern.

Step 2 — Classify each branch

For every candidate origin/<branch>:

A — unique file count (three-dot diff from merge-base):

git diff --name-only origin/develop...origin/<branch> | wc -l

B — files ONLY in the branch (not in develop):

git diff --name-only --diff-filter=A origin/develop origin/<branch>

Classify as:

• EMPTY — A = 0 AND B = 0 → branch adds nothing, safe to delete
• COVERED — B > 0 but every file in B is already present in a known feature branch → safe to reset
• HAS_UNIQUE — B > 0 with at least one file not in any feature branch → must rescue first

Step 3 — Handle EMPTY branches

These branches were never extended beyond the old fork point.

git push origin --delete <branch>

Step 4 — Handle COVERED branches

All unique files are already captured in a feature branch we are keeping. Reset the branch to develop HEAD so it is current but carries no stale code.

git push origin origin/develop:refs/heads/<branch> --force

Step 5 — Handle HAS_UNIQUE branches

Rescue uncovered files before resetting.

5a — Identify which feature branch the files belong to

Group uncovered files by module/domain:

• Modules/Foo/… → belongs to whatever feature owns Foo
• If unclear, create a new feature branch named after the owning issue/feature

5b — Extract files onto the correct feature branch

On the target feature branch (must already exist and be ahead of develop):

git checkout origin/<stale-branch> -- <uncovered-file1> <uncovered-file2> ...
git add <files>
git commit -m "chore: rescue <description> from stale <stale-branch>"
git push origin HEAD --force-with-lease

If the target feature branch does not yet exist, use the feature-branch-extraction procedure to create it properly on top of develop HEAD first.

5c — Reset the stale branch to develop

git push origin origin/develop:refs/heads/<branch> --force

Step 6 — Verify

# Confirm each branch is now equal to develop
for branch in <cleaned-branches>; do
  ahead=$(git rev-list origin/develop..origin/$branch --count)
  behind=$(git rev-list origin/$branch..origin/develop --count)
  echo "$branch → ahead=$ahead behind=$behind"
done

Expected: all cleaned branches show ahead=0 behind=0.

Notes

• Only force-push to branches that are NOT open PRs unless the PR is yours and you
  intend to update it.
• GitHub Copilot branches (copilot/*) are AI-generated; resetting them is safe —
  Copilot will recreate them if needed.
• The --diff-filter=A flag catches files the branch adds that develop lacks.
  Files the branch modifies relative to develop but which also exist in develop
  are not "unique" — develop's version is preferred.
• Run git fetch --prune first so local remote-tracking refs are current.