git-store-modes

#!/usr/bin/env bash

set -o errexit -o nounset -o pipefail

DFLT_MODEFILE='.git-mode-cache'
USAGE="Usage:
    ${0##*/} save OPTIONS
or  ${0##*/} restore OPTIONS

Save or restore permissions of files in a git repository.

Options:
  -f file:  Save permissions to (or load from) file (default: ${DFLT_MODEFILE})
            Note: if a relative path is supplied, it is interpreted relative to
            the repository root.
  -h:       Show this help and exit.
"

function go_worktree_root() {
  local CDUP
  CDUP=$(git rev-parse --show-cdup)

  cd "${CDUP}"
}

function files_ancestors() {
  local FPATH

  while read -r -d '' FPATH; do
    printf '%s\0' "${FPATH}"

    while [[ "${FPATH}" && "${FPATH}" == */* ]]; do
      FPATH="${FPATH%/*}"
      printf '%s\0' "${FPATH}"
    done
  done
}

function filter_symlinks() {
  local FILENAME

  while read -r -d '' FILENAME; do
    if [[ -a "${FILENAME}" && ! -L "${FILENAME}" ]]; then
      printf '%s\0' "${FILENAME}"
    fi
  done
}

function get_modes() {
  local -a STATOPTS=(--printf '%a\t%n\0')
  local STAT

  if stat --printf '' . &> /dev/null; then
    STAT=stat
  else
    STAT=gstat
  fi

  git ls-files -cz --full-name \
    | files_ancestors \
    | filter_symlinks \
    | sort -zu \
    | xargs -0 "${STAT}" "${STATOPTS[@]}"
}

function restore_modes() {
  local MODE
  local FILENAME

  trap IFS="${IFS}" RETURN
  printf -v IFS '\t'

  while read -r -d '' MODE FILENAME; do
    if [[ -a "${FILENAME}" && ! -L "${FILENAME}" ]]; then
      chmod "${MODE}" "${FILENAME}"
    fi
  done
}

function process_args() {
  local OPTIND=1
  local -n CMD=$1
  local -n FNAME=$2

  CMD="${3^^*}"
  FNAME="${DFLT_MODEFILE}"

  shift 3

  while getopts 'f:h' OPT; do
    case "${OPT}" in
      'f')
        FNAME=${OPTARG}
        ;;
      'h')
        echo "${USAGE}" >&2
        exit
        ;;
      *)
        echo "${USAGE}" >&2
        exit 1
        ;;
    esac
  done

  shift $((OPTIND-1))

  if [[ $# -gt 0 ]]; then
    echo "Unexpected arguments: $@" >&2
    echo "${USAGE}" >&2
    exit 1
  fi
}

function main() {
  local COMMAND
  local MODEFILE

  process_args COMMAND MODEFILE "$@"

  go_worktree_root

  case "${COMMAND}" in
    'SAVE')
      get_modes > "${MODEFILE}"
      if [[ -f "${MODEFILE}" ]]; then
        git add "$MODEFILE"
      fi
      ;;

    'RESTORE')
      restore_modes < "${MODEFILE}"
      ;;

    *)
      echo "${USAGE}" >&2
      exit 1
      ;;
  esac
}

main "$@"