#!/bin/bash
#
# Rewrite identities in commits.
#

# Parameters
BASENAME="`basename $0`"
OLD_EMAIL="$1"
NEW_EMAIL="$2"

# Syntax check
if [ -z "$3" ]; then
  echo "usage: $BASENAME <old-email> <new-email> <new-name>"
  exit 1
fi

# Get new name
shift 2
NEW_NAME="$*"

# Apply filter
echo "Please run this command:"
echo ""
cat <<-EOF
git filter-branch --commit-filter '
      if [ "\$GIT_AUTHOR_EMAIL" = "$OLD_EMAIL" ];
      then
              GIT_AUTHOR_NAME="$NEW_NAME";
              GIT_AUTHOR_EMAIL="$NEW_EMAIL";
              git commit-tree "\$@";
      else
              git commit-tree "\$@";
      fi' HEAD
EOF

# See https://stackoverflow.com/questions/7654822
echo "Done! Check results and remove the backup once you're ready:"
echo "git update-ref -d refs/original/refs/heads/master"