.mailmap file may be created in any text editor and is just a plain text file containing optional contributor names, primary email addresses, and their aliases. it has to be placed in the project's root, next to the
Keep in mind that this just modifies the visual output of commands like
git shortlog or
git log --use-mailmap. This will not rewrite commit history or prevent commits with varying names and/or email addresses.
To prevent commits based on information such as email addresses, you should use git hooks instead.