unixorn/git-extra-commands

#!/usr/bin/env bash
#
# Rewrite all commits with one name to use another
#
# From https://stackoverflow.com/a/40565934

set -o pipefail
if [[ -n "$DEBUG" ]]; then
  set -x
fi

fail() {
  printf '%s\n' "$1" >&2  ## Send message to stderr. Exclude >&2 if you don't want it that way.
  exit "${2-1}"  ## Return a code specified by $2 or 1 by default.
}

function has() {
  which "$@" > /dev/null 2>&1
}

if ! has git-filter-branch; then
  myname=$(basename "$0")
  fail "Usage: $myname OLDNAME NEW_NAME NEW_EMAIL"
fi

DEFAULT_NAME="$(git config user.name)"
DEFAULT_EMAIL="$(git config user.email)"
export OLD_NAME="${1:-$DEFAULT_NAME}"
export NEW_NAME="${2:-$DEFAULT_NAME}"
export NEW_EMAIL="${3:-$DEFAULT_EMAIL}"

echo "Old: $OLD_NAME <*>"
echo "New: $NEW_NAME <$NEW_EMAIL>"
echo "To undo, use: git reset $(git rev-parse HEAD)"

exec git filter-branch --env-filter \
'if [ "$GIT_AUTHOR_NAME" = "${OLD_NAME}" ]; then
    export GIT_AUTHOR_NAME="${NEW_NAME}"
    export GIT_AUTHOR_EMAIL="${NEW_EMAIL}"
    export GIT_COMMITTER_NAME="${NEW_NAME}"
    export GIT_COMMITTER_EMAIL="${NEW_EMAIL}"
fi'