git-commit-with-mtime

#!/bin/sh -e
# SPDX-License-Identifier: WTFPL
# shellcheck enable=

usage () {
	cat <<- EOF
		usage: $0 FILE [GIT-COMMIT ARGS...]

		git add FILE and create a commit that will have author date set to the last modification time (mtime) of FILE.
		Arguments passed after file are optional and will be passed to git-commit.
		Example: $0 foo.txt -m 'introduce foo.txt'
	EOF
}

if [ $# -lt 1 ]
then
	usage >&2
	exit 64  # EX_USAGE
elif [ "$1" = -h ]
then
	usage
	exit 0
fi

file="$1"
shift

fdate=$(date -r "$file")

git add "$file"
git commit --date "$fdate" "$@"