Sets file mtimes to latest git commit timestamp

git_set_mtimes.sh

# Ensures mtimes are consistent with the git commit to utilize ADD caching
# Re-written from https://github.com/docker-library/official-images/blob/1dd9118804a06fef308e613cdbabe44bf0529043/bashbrew/git-set-mtimes
# This version is more platform compatible (assuming you have ruby), works on os x and *nix
git_set_mtimes() {
  pushd $1
  IFS=$'\n'
  files=( $({ git ls-files | xargs dirname | sort -u && git ls-files; } | sort -r) )
  unset IFS
  for f in "${files[@]}"; do
    stamp="$(git --no-pager log -1 --format='format:%ai' -- "$f")"
    tstamp=$(echo $stamp | ruby -r 'date' -ne 'puts DateTime.parse($_).strftime("%Y%m%d%H%M.%S")')
    touch -h -t "$tstamp" "$f"
  done
  popd
}