Bash scripts for amending author of commits at once

git-amend-author.sh

#!/bin/bash

# (for example, your previous author name contains `Anonymous`)
# @ PROJECT_ROOT dir: run
#
# git log | grep -B 1 "Anonymous" | grep commit | awk '{print $2}' | xargs -L 1 ./git-amend-author.sh

if [ "$#" -ne 1 ]; then
    echo "Illegal number of parameters: $#"
    exit 1
fi

prev_hash=$1

new_author="John Doe <[email protected]>" # edit this variable for you
git checkout $prev_hash && git commit --amend --no-edit --author "$new_author"

ret_val=$?
if [ $ret_val -ne 0 ]; then
    echo "`git commit --amend` failed"
    exit 1
fi

new_hash=`git rev-parse HEAD`

git checkout master && git replace $prev_hash $new_hash

ret_val=$?
if [ $ret_val -ne 0 ]; then
    echo "`git commit --amend` failed"
    exit 1
fi

git filter-branch -f -- --all && git replace -d $prev_hash

echo "Successfully amended a git commit."