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From:   Junio C Hamano <gitster@pobox.com>
To:     "Hedges Alexander" <ahedges@student.ethz.ch>
Cc:     "git\@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: Feature Request: Branch-Aware Submodules
References: <7B5AD16B-9729-453E-839C-2A2FDB07F8E9@student.ethz.ch>
Date:   Thu, 25 Aug 2016 10:46:18 -0700
In-Reply-To: <7B5AD16B-9729-453E-839C-2A2FDB07F8E9@student.ethz.ch> (Hedges
        Alexander's message of "Thu, 25 Aug 2016 09:00:47 +0000")
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"Hedges  Alexander" <ahedges@student.ethz.ch> writes:

> Right now updating a submodule in a topic branch and merging it into master
> will not change the submodule index in master leading to at least two commit
> for the same change (one in any active branch).

I stopped reading here because I am not getting this.

I guess I am confused because I do not understand what you mean by
"the submodule index in master".  The concept of "index" does not
belong to each branch (or even a commit), so by "index" you are
trying to point at something else, but I cannot guess what it is.

You have a top-level superproject that has another project as its
submodule.  The superproject has topic and master branches (or it
may only have master).  The project that is used as its submodule
also has topic and master branches (it may have more).  You do your
development in the submodule, e.g.

    cd submoduledir
    git checkout topic
    hack hack hack
    git commit
    git checkout master
    git merge topic

and merge the topic branch into its master when the topic is
polished enough.

And then?  The 'master' in the submodule is good enough, so you'd
go back to the top-level superproject and bind that merged result 
in its place?  e.g.

    cd ..
    git add submoduledir
    git commit -m "Updated submoduledir with the topic"

That is only one commit each in the superproject and the submodule
project.