git-rewrite-author.sh

git filter-branch -f --env-filter '    
  if test "$GIT_AUTHOR_EMAIL" != "$GIT_COMMITTER_EMAIL"
  then
    GIT_COMMITTER_EMAIL="$GIT_AUTHOR_EMAIL"
  fi
  if test "$GIT_AUTHOR_NAME" != "$GIT_COMMITTER_NAME"
  then
    GIT_COMMITTER_NAME="$GIT_AUTHOR_NAME"
  fi' master..HEAD

A script to take a branch and rewrite the committer to be the author (for when you take someone else’s branch and rebase it for them). Assumes you have a master branch locally and have the branch you want to modify checked out, and that master is an ancestor of the branch.