Delete Squash-merged local Git Branches

A node utility to delete local branches that have already been merged into a mainline via the squash-merge strategy. (Frequently used on Github.)

With normal merge commits, you can run git branch --merged to get a list of already-merged branches, but with squash-merge you end up with new commits that contain your feature branch's work.

This util will find those already-squashed-and-merged branches and optionally delete them.

Explanation of what's going on under the hood

• Gets the branch list by name
  • git for-each-ref refs/heads/ --format=%(refname:short)
• Then for each branch found:
  • Find the ancestor commit where ThisBranch left BaseBranch
    • git merge-base <BaseBranch> <ThisBranch>
  • Get the tree ID
    • git rev-parse <ThisBranch>^{tree}
  • Make up a temporary commit with the contents ThisBranch squashed together
    • git commit-tree <TreeID> -p <AncestorSha> -m "Temp <ThisBranch>"
  • See if the temp commit contents was already applied to upstream
    • git cherry <BaseBranch> <TempPatchSha>
  • If the above output starts with - the branch is a candidate for deletion

Usage:

By default, this utility runs in dry mode. You will be prompted if you actually want to run any destructive changes.

The easiest way to use github-loppers is via NPX:

cd ~/code/myProject                                # Get to your local repo
npx https://github.com/betaorbust/github-loppers   # Run the utility

which will temporarily fetch the dependencies and run github-loppers so you can either list out or delete your stale branches.

Requirements:

• Node >= 18.18.0
• Git
• That the mainline branch your checking against is checked out locally.

Acknowledgments

Git logic from @not-an-aardvark's awesome implementation.