restore_timestamp_fromgit.sh

#!/bin/sh -e

OS=${OS:-`uname`}
old_rev="$1"
new_rev="$2"

get_file_rev() {
    git rev-list -n 1 "$new_rev" "$1"
}


filename=README.md
rev=$(git log --oneline | head -n 1 | awk '{ print $1 }')
abbrev_commit=$(git rev-list -n 1 ${rev} ${filename})
time_in_millis=$(git show --pretty=format:%at --abbrev-commit ${abbrev_commit} | head -n 1)
file_time=$(date -r ${time_in_millis} '+%Y%m%d%H%M.%S')
echo "$file_time"
touch -h -t "${file_time}" "${filename}"

if   [ "$OS" = 'Linux' ]
then
    update_file_timestamp() {
        file_time=`git show --pretty=format:%ai --abbrev-commit "$(get_file_rev "$1")" | head -n 1`
        touch -d "$file_time" "$1"
    }
elif [ "$OS" = 'FreeBSD' ]
then
    update_file_timestamp() {
        file_time=`date -r "$(git show --pretty=format:%at --abbrev-commit "$(get_file_rev "$1")" | head -n 1)" '+%Y%m%d%H%M.%S'`
        touch -h -t "$file_time" "$1"
    }
else
    echo "timestamp changing not implemented" >&2
    update_file_timestamp() {
        echo "update_file_timestamp $1"
        file_time=`date -r "$(git show --pretty=format:%at --abbrev-commit "$(get_file_rev "$1")" | head -n 1)" '+%Y%m%d%H%M.%S'`
        echo "update_file_timestamp $file_time"
    }
#    exit 1
fi

IFS=`printf '\t\n\t'`

rev=$(git log --oneline | head -n 1 | awk '{ print $1 }')
git ls-files | while read -r filename
do
    echo ${filename}
    abbrev_commit=$(git rev-list -n 1 "${rev}" "${filename}")
    #time_in_millis=$(git show --pretty=format:%at --abbrev-commit "${abbrev_commit}" | head -n 1)

    file_time=`git show --pretty=format:%ai --abbrev-commit "$abbrev_commit" | head -n 1`
#    time_in_millis=$(git show --pretty=format:%ai --abbrev-commit "${abbrev_commit}" | head -n 1)
#    file_time=$(date -r "${time_in_millis}" '+%Y%m%d%H%M.%S')
    echo "file_time=${file_time}"
    echo "file_name=${filename}"
    ll -a "${filename}"
#    touch -h -t "${file_time}" "${filename}"
    touch -d "${file_time}" "${filename}"
    ll -a "${filename}"
done