git_backup.sh

#!/usr/bin/env bash

# config

date=`date "+%Y-%m-%d"`
git_binary=/usr/local/bin/git

# repositories in /git, space-separated.
repos="foo.git bar.git"


# back up repositories

cd /git
for repo in $repos
do
  tar -czf /git/backup/${repo}-${date}.tar.gz ${repo}
done


# garbage-collect; reclaim disk space and optimize for performance
#
# NOTE: there is a GOOD REASON we do this AFTER backing up:
#       if you accidentally deleted a branch or something, there might still be traces of it left before garbage-collecting.
#       after running 'git gc', those traces are gone forever.

for repo in $repos
do
  cd /git/${repo} && $git_binary gc --quiet
done