Archive Git branches in remote that have not received a commit for x days/weeks/months/years

archive-old-branches.sh

#!/usr/bin/env bash

set -euo pipefail

declare -a branches=()

# Update our view of the remote
git fetch --all

# Read in names of branches in remote (<remote-name>/<branch-name>), excluding already-archived branches
# Also filter by whether the branch received any commits during a recent time-interval
while read -r branch; do
    if [ -z "$(git log -1 --since='6 months ago' -s "${branch}")" ]; then
        branches+=( "$branch" )
    fi
done < <(git branch -r | grep -vF HEAD | grep -vF -- '->' | grep -vF '/archive/' | sed -e 's/^\s\+\|\s\+$//g')

# List branches and last commit relative-time
echo ""
echo "Branches:"
for branch in "${branches[@]}"; do
    printf -- " * %s \x1b[35m(%s ago)\x1b[0m\n" "${branch}" "$(git log -1 --format="%cr" "$branch")"
done
echo ""

# Ask for confirmation
if ! read -r -n 1 -p 'Archive these branches? ' yn || ! [[ $yn == [Yy] ]]; then
    echo "Cancelled"
    exit 1
fi

# Iterate over branches and prefix their names with "archive/"
function do_archiving {
    local remote_name
    local local_name
    local archive_name
    local worktree
    worktree="$(mktemp -u)"
    for branch in "${branches[@]}"; do
        remote_name="$(printf -- "%s\n" "$branch" | cut -d/ -f1)"
        local_name="$(printf -- "%s\n" "$branch" | cut -d/ -f2-)"
        archive_name="archive/${local_name}"
        git worktree add -b "${archive_name}" "$worktree" "${branch}"
        pushd "$worktree"
        git push "${remote_name}" ":${local_name}" "${archive_name}:${archive_name}"
        popd
        git worktree remove -f "$worktree"
        rm -rf "$worktree"
        git branch -D "${archive_name}"
    done | tee .archive-old-branches.log
}

do_archiving