How can I delete all git branches which have been "Squash and Merge" via GitHub?

Question

Ever since GitHub introduced Squash and Merge, all the cool kids at my workplace are using it when merging pull requests. Is there a way to cleanup "Squash and Merge" branches?

The following command from How can I delete all git branches which have been merged? does not work for "Squash and Merge":

git branch --merged | egrep -v "(^\*|master|dev)" | xargs git branch -d 

Answer 1

Here's a script that will delete all local branches that have been squash merged into master:

git checkout -q master && git for-each-ref refs/heads/ "--format=%(refname:short)" | while read branch; do mergeBase=$(git merge-base master $branch) && [[ $(git cherry master $(git commit-tree $(git rev-parse "$branch^{tree}") -p $mergeBase -m _)) == "-"* ]] && git branch -D $branch; done 

If you want to run a dry run, you can instead run this:

git checkout -q master && git for-each-ref refs/heads/ "--format=%(refname:short)" | while read branch; do mergeBase=$(git merge-base master $branch) && [[ $(git cherry master $(git commit-tree $(git rev-parse "$branch^{tree}") -p $mergeBase -m _)) == "-"* ]] && echo "$branch is merged into master and can be deleted"; done 

You can then setup an alias like this:

alias gprunesquashmerged='git checkout -q master && git for-each-ref refs/heads/ "--format=%(refname:short)" | while read branch; do mergeBase=$(git merge-base master $branch) && [[ $(git cherry master $(git commit-tree $(git rev-parse "$branch^{tree}") -p $mergeBase -m _)) == "-"* ]] && git branch -D $branch; done' 

Source:

https://github.com/not-an-aardvark/git-delete-squashed