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From:   Junio C Hamano <gitster@pobox.com>
To:     Uma Srinivasan <usrinivasan@twitter.com>
Cc:     git@vger.kernel.org
Subject: Re: git submodules implementation question
References: <CAN5XQftQH8B+hWVh4JQgZwAp+rkbz51P5NZDc_+Tfm0EB1zkew@mail.gmail.com>
Date:   Mon, 29 Aug 2016 13:03:10 -0700
In-Reply-To: <CAN5XQftQH8B+hWVh4JQgZwAp+rkbz51P5NZDc_+Tfm0EB1zkew@mail.gmail.com>
        (Uma Srinivasan's message of "Sun, 28 Aug 2016 16:24:54 -0700")
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Uma Srinivasan <usrinivasan@twitter.com> writes:

> git_dir = read_gitfile(buf.buf);
> if (!git_dir)
>
>                 git_dir = buf.buf;
>
> Can anyone explain to me why we are replacing a failed reading of a
> git file with the original sub directory name?

A top-level superproject can have a submodule bound at its "dir/"
directory, and "dir/.git" can either be a gitfile which you can read
with read_gitfile() and point into somewhere in ".git/modules/" of
the top-level superproject.  "dir/.git" can _ALSO_ be a fully valid
Git directory.  So at the top of a superproject, you could do

	git clone $URL ./dir2
        git add dir2

to clone an independent project into dir2 directory, and add it as a
new submodule.  The fallback is to support such a layout.