git/Documentation/mailmap.txt

If the file `.mailmap` exists at the toplevel of the repository, or at
the location pointed to by the mailmap.file configuration option, it
is used to map author and committer names and email addresses to
canonical real names and email addresses.

In the simple form, each line in the file consists of the canonical
real name of an author, whitespace, and an email address used in the
commit (enclosed by '<' and '>') to map to the name. For example:
--
	Proper Name <commit@email.xx>
--

The more complex forms are:
--
	<proper@email.xx> <commit@email.xx>
--
which allows mailmap to replace only the email part of a commit, and:
--
	Proper Name <proper@email.xx> <commit@email.xx>
--
which allows mailmap to replace both the name and the email of a
commit matching the specified commit email address, and:
--
	Proper Name <proper@email.xx> Commit Name <commit@email.xx>
--
which allows mailmap to replace both the name and the email of a
commit matching both the specified commit name and email address.

Example 1: Your history contains commits by two authors, Jane
and Joe, whose names appear in the repository under several forms:

------------
Joe Developer <joe@example.com>
Joe R. Developer <joe@example.com>
Jane Doe <jane@example.com>
Jane Doe <jane@laptop.(none)>
Jane D. <jane@desktop.(none)>
------------

Now suppose that Joe wants his middle name initial used, and Jane
prefers her family name fully spelled out. A proper `.mailmap` file
would look like:

------------
Jane Doe         <jane@desktop.(none)>
Joe R. Developer <joe@example.com>
------------

Note how there is no need for an entry for <jane@laptop.(none)>, because the
real name of that author is already correct.

Example 2: Your repository contains commits from the following
authors:

------------
nick1 <bugs@company.xx>
nick2 <bugs@company.xx>
nick2 <nick2@company.xx>
santa <me@company.xx>
claus <me@company.xx>
CTO <cto@coompany.xx>
------------

Then you might want a `.mailmap` file that looks like:
------------
<cto@company.xx>                       <cto@coompany.xx>
Some Dude <some@dude.xx>         nick1 <bugs@company.xx>
Other Author <other@author.xx>   nick2 <bugs@company.xx>
Other Author <other@author.xx>         <nick2@company.xx>
Santa Claus <santa.claus@northpole.xx> <me@company.xx>
------------

Use hash '#' for comments that are either on their own line, or after
the email address.