Git's environment filter

This is a thing I keep on forgetting although I've done it several times. So, I'm writing a blog post hoping it will help me memorize this.

So... how do you rewrite Git's history, specifically the environment variables. With git filter-branch of course. I frequently need it in order to change the author and committer email addresses (either from personal to work or the other way around).

git filter-branch --env-filter 'export GIT_AUTHOR_EMAIL=""' HEAD
git filter-branch --env-filter 'export GIT_COMMITTER_EMAIL=""' HEAD

Don't forget that there are two email addresses, OK? The author's and committer's one. Oh, and no spaces around the equal sign.

For a more complicated situation see this answer on