Rewrite target author and commiter name/email/date with data from source commit

git-rewrite-source-target.sh

#!/bin/sh
# Rewrite's the commit with data from source commit

echo "WARNING: Your TARGET_COMMIT must have in your current branch."

SOURCE_COMMIT=$1
TARGET_COMMIT=$2

SOURCE_COMMIT=$(git rev-parse $SOURCE_COMMIT)
if [ $? -ne 0 ]; then
  echo "Your SOURCE_COMMIT ($SOURCE_COMMIT) doesn't exists."
  exit 1
fi

TARGET_COMMIT=$(git rev-parse $TARGET_COMMIT)
if [ $? -ne 0 ]; then
  echo "Your TARGET_COMMIT ($TARGET_COMMIT) doesn't exists."
  exit 1
fi

# Warning: POTENTIALLY DESTRUCTIVE!
rm -Rf .git/refs/original

echo "Rewriting $SOURCE_COMMIT data to $TARGET_COMMIT"

MESSAGE=$(git log --pretty="%s" -1 $SOURCE_COMMIT)
AUTHOR_NAME=$(git log --pretty="%an" -1 $SOURCE_COMMIT)
AUTHOR_EMAIL=$(git log --pretty="%ae" -1 $SOURCE_COMMIT)
AUTHOR_DATE=$(git log --pretty="%ad" -1 $SOURCE_COMMIT)
COMMITER_NAME=$(git log --pretty="%cn" -1 $SOURCE_COMMIT)
COMMITER_EMAIL=$(git log --pretty="%ce" -1 $SOURCE_COMMIT)
COMMITER_DATE=$(git log --pretty="%cd" -1 $SOURCE_COMMIT)

git filter-branch --env-filter \
    'if [ "'"$TARGET_COMMIT"'" == "$GIT_COMMIT" ]; then
       export GIT_AUTHOR_NAME="'"$AUTHOR_NAME"'";
       export GIT_AUTHOR_EMAIL="'"$AUTHOR_EMAIL"'";
       export GIT_AUTHOR_DATE="'"$AUTHOR_DATE"'";
       export GIT_COMMITTER_NAME="'"$COMMITER_NAME"'";
       export GIT_COMMITTER_EMAIL="'"$COMMITER_EMAIL"'";
       export GIT_COMMITTER_DATE="'"$COMMITER_DATE"'";
     fi'