Script to remove local PR branches after the PRs have been squash merged

trim-branches.sh

#!/bin/bash
#
# Removes local branches whose contents have already been merged into main.
#
set -eo pipefail

say() {
    echo ===
    echo === "$@"
    echo ===
}

if git diff --exit-code --quiet; then
    :
else
    echo "Repo is dirty! Aborting to avoid screwing it up." 1>&2
    exit 1
fi

TEMP_BRANCH=trim.$$
LOG=/tmp/trim.$$.out

say "Updating main"

git checkout main
git pull --rebase -p

missing_remotes=$(git branch -vv | cut -c3- | awk '/: gone]/ { print $1 }')

for branch in $missing_remotes; do
    say "Trying to trim $branch"

    git checkout -f -B $TEMP_BRANCH "$branch"
    git reset --soft $(git merge-base HEAD main)

    git commit -a -m 'Dummy commit to check for squash merge'

    if git rebase main > /dev/null 2> /dev/null; then
        if git diff --quiet main; then
            say "$branch is fully merged; deleting it"
            git branch -D "$branch"
        else
            say "$branch is not fully merged"
        fi
    else
        say "!!!!!! Failed to rebase $branch on main !!!!!!"

        git rebase --abort
    fi
done

git checkout main
git branch -D "$TEMP_BRANCH"