#!/bin/bash

set -eu

function usage {
    echo "Usage: $0 [--remote origin] [--age ndays]"
    echo
    echo "This tool will not change your repository, the output is a list of git push commands you can use to delete old branches."
    echo
    echo "Note that the arguments must be passed in the order listed above."
    exit 1
}

if [ "${1:-}" = "--help" ]; then
    usage
fi

remote="origin"
if [ "${1:-}" = "--remote" ]; then
    remote="$2"
    shift
    shift
fi

age_days=30
if [ "${1:-}" = "--age" ]; then
    age_days="$2"
    shift
    shift
fi
age_seconds=$((age_days*24*3600))

if [ -n "${1:-}" ]; then
    usage
fi


echo "## Fetching latest changes from $remote"
git fetch -p "${remote}"


echo "## Constructing list of revisions in master and tags"
safe_revs_file="$(mktemp -t gitcleanup.XXXXXX)"
git rev-list origin/master --tags > "$safe_revs_file"


echo "## Checking for branches to delete"
now="$(date +%s)"
git ls-remote --heads "$remote" | while read line; do
    set $line
    rev="$1"
    branch="$2"
    timestamp="$(git rev-list --format=format:'%ct' --max-count=1 "$rev"|tail -n1)"
    age=$((now-timestamp))

    if [ "$branch" = "refs/heads/master" ]; then
        continue;
    fi

    if grep -q "$rev" "$safe_revs_file"; then
        echo git push "$remote" ":$branch" "# remove merged into master or tag"
        continue
    fi

    if [ "$age" -gt "$age_seconds" ]; then
        branch_name="${branch##refs/heads/}"
        echo git tag "archived/$branch_name" "$rev" "# create tag for older than $age_days days branch"
        echo git push "$remote" tag "archived/$branch_name" "# push tag for older than $age_days days branch"
        echo git push "$remote" ":$branch" "# remove older than $age_days days"
        continue
    fi
done

rm -f "$safe_revs_file"