git-list-obsolete-branches.sh

#!/bin/bash

set -eu

master=upstream/master
ourremote=origin
ignore_pattern="^pr/|^(master|develop)$"
skip_pattern="^(test|draft)/"

candidates=()
skipped=()

echo "Checking branches..."

while read branch stat remote; do
    if [[ $branch =~ $ignore_pattern ]]; then
        continue
    elif [[ $remote != $ourremote || $branch =~ $skip_pattern ]]; then
        skipped+=($branch)
        continue
    elif [[ $stat = "[]" && $remote != "" ]]; then
        # disabled because now we encourages "git push -d" for candidates.
        # use "purged-branches" alias instead.
        continue
        #candidates+=($branch)
        #echo $branch: upstream deleted
    elif git merge-base --is-ancestor $branch $master; then
        candidates+=($branch)
        echo $branch: merged
    else
        # check squash merge state
        mergeBase=$(git merge-base $master $branch)
        squashed=$branch
        if [[ $(git rev-parse $branch^) != $mergeBase ]]; then
            squash=$(git commit-tree $(git rev-parse $branch^{tree}) -p $mergeBase -m _)
        fi
        if [[ $(git cherry $master $squashed) == "-"* ]]; then
            candidates+=($branch)
            echo $branch: squash merged
        else
            echo "# $branch: looks active"
        fi
    fi
done < <(git for-each-ref --format '%(refname:short) [%(upstream:trackshort)] %(upstream:remotename)' refs/heads)

echo "Done."

if (( ${#skipped[@]} )); then
    echo ""
    echo "Note that below branches were skipped:"
    printf " %s\n" ${skipped[@]}
fi

echo ""

if (( ${#candidates[@]} )); then
    echo "To remove all candidate branches from remote, run this:"
    echo ""
    echo "git push $ourremote -d ${candidates[@]}"
else
    echo "No obsolete branches were detected."
fi