Delete branches that have been merged to the branch of your choice. Works with regular merges and squash merges.

git-delete-merged-branches.sh

#!/bin/sh

set -eo pipefail

BASE=origin/dev

if [[ $1 == "-d" ]]; then
    DELETE=1
    shift
fi

if [[ -n "$1" ]]; then
    BASE=$1
    #echo "base = $1"
fi

if [[ -z "$DELETE" ]]; then
    echo "Finding branches merged to: $BASE"
    echo "Run with -d to delete them"
else
    echo "Deleting branches merged to: $BASE"
fi

echo

#-------------------------------------------------------

# Return success if the branch should be excluded
isExcluded()
{
    case $1 in
        master|hotfix|dev|RELEASE-*)
            return 0
            ;;
        *)
            return 1
            ;;
    esac
}

# Delete the branch or warn that it would be deleted
deleteBranch()
{
    if [[ -z "$DELETE" ]]; then
        echo "Would delete: $(git rev-parse --short $1) $1"
    else
        #echo "Deleting: $(git rev-parse --short $1) $1"
        git branch -D $1
    fi
}

#-------------------------------------------------------

# Regular merges
for branch in `git branch --merged $BASE`; do
    isExcluded $branch && continue
    deleteBranch $branch
done

# Cherry-picked branches
git for-each-ref refs/heads/ "--format=%(refname:short)" | while read branch; do
    # Exclude branches we don't ever want to delete
    isExcluded $branch && continue

    mergeBase=$(git merge-base $BASE $branch)
    if [[ $(git cherry $BASE $(git commit-tree $(git rev-parse $branch\^{tree}) -p $mergeBase -m _)) == "-"* ]]; then
        deleteBranch $branch
    fi
done