#!/usr/bin/env bash
#
# Change files modification time to their last commit date
#

if [ "$1" = --touch ]; then
  # Internal use option only just to parallelize things.
  shift
  for f; do
    t=$(git --no-pager log --no-renames --pretty=format:%cI -1 @ -- "$f" 2>/dev/null)
    if [ -n "$t" ]; then
      echo "+ touch -d $t $f" >&2
      touch -d "$t" "$f"
    fi
  done
else
  # `-n` should be limited or parallelization will not give effect,
  # because all args will go into single worker.
  NPROC=$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || getconf _NPROCESSORS_ONLN 2>/dev/null)
  git ls-tree -z -r -t --name-only @ \
  | xargs -0 -P${NPROC:-1} -n${NPROC:-1} -r git utimes --touch
fi