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From:   Junio C Hamano <gitster@pobox.com>
To:     Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc:     Jeff King <peff@peff.net>, git@vger.kernel.org,
        David Aguilar <davvid@gmail.com>,
        Dennis Kaarsemaker <dennis@kaarsemaker.net>
Subject: Re: [PATCH v3 1/2] difftool: add a skeleton for the upcoming builtin
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Date:   Mon, 05 Dec 2016 10:37:39 -0800
In-Reply-To: <alpine.DEB.2.20.1612051126320.117539@virtualbox> (Johannes
        Schindelin's message of "Mon, 5 Dec 2016 11:36:19 +0100 (CET)")
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Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Seriously, do you really think it is a good idea to have
> git_config_get_value() *ignore* any value in .git/config?

When we do not know ".git/" directory we see is the repository we
were told to work on, then we should ignore ".git/config" file.  So
allowing git_config_get_value() to _ignore_ ".git/config" before the
program calls setup_git_directory() does have its uses.

But I agree that "difftool.useBuiltin" that flips between two
implementations is a different use case than the above.  Both
implementations eventually want to work on ".git/" and would
want to read from ".git/config".

> We need to fix this.

I have a feeling that "environment modifications that cannot be
undone" we used as the rationale in 73c2779f42 ("builtin-am:
implement skeletal builtin am", 2015-08-04) might be overly
pessimistic and in order to implement undo_setup_git_directory(),
all we need to do may just be matter of doing a chdir(2) back to
prefix and unsetting GIT_PREFIX environment, but I haven't looked
into details of the setup sequence recently.