Subject: What's the ".git/gitdir" file?

From: Kyle Meyer <[email-masked]>
Date: Tue, 27 Oct 2015 18:04:46 -0400

Hello,

When a ".git" file points to another repo, a ".git/gitdir" file is
created in that repo.

For example, running

    $ mkdir repo-a repo-b
    $ cd repo-a
    $ git init
    $ cd ../repo-b
    $ echo "gitdir: ../repo-a/.git" > .git
    $ git status

results in a file "repo-a/.git/gitdir" that contains

    $ cat repo-a/.git/gitdir
    .git

I don't see this file mentioned in the gitrepository-layout manpage,
and my searches haven't turned up any information on it.  What's the
purpose of ".git/gitdir"?  Are there cases where it will contain
something other than ".git"?

Thanks.

--
Kyle
git version 2.6.1