Re: [PATCH] Display change history as a diff between two dirs

From: Junio C Hamano <gitster@pobox.com>
Date: Nov 1, 2011, 17:15 UTC
Message-ID: <7vr51rn4qc.fsf@alter.siamese.dyndns.org>
In-Reply-To: <CANEMaQRoXRygmrYsu0xF6mWq50r9Qhh-YuXXNAhyQewd+fDtsQ@mail.gmail.com>

Roland Kaufmann <rlndkfmn+git@gmail.com> writes:

Show 13 quoted lines

> On Tue, Nov 1, 2011 at 04:49, Junio C Hamano <gitster@pobox.com> wrote:
>> Roland Kaufmann <rlndkfmn+git@gmail.com> writes:
>>> Would it be better to have yet another configuration available for
>>> this option instead of reusing the existing infrastructure for `git
>>> difftool`?
>
>> It probably is OK for "git diff --dirdiff" to use GIT_EXTERNAL_TREEDIFF if
>> and only if GIT_EXTERNAL_DIFF is not defined, and use GIT_EXTERNAL_DIFF
>> otherwise. People who have GIT_EXTERNAL_DIFF set to a tool capable of
>> handing directory pair can just add "--dirdiff" to the command line, and
>
> Did you perhaps mean the other way around: GIT_EXTERNAL_TREEDIFF
> if set, and GIT_EXTERNAL_DIFF otherwise?

I think I misstated the precedence order. What I had in mind was roughly like this:

 1. "git diff" (and others like "git log") without "--dirdiff" option:
    GIT_EXTERNAL_DIFF is used just as before and no GIT_EXTERNAL_TREEDIFF
    is consulted;

 2. "git diff --dirdiff": GIT_EXTERNAL_TREEDIFF is used if set, otherwise
    GIT_EXTERNAL_DIFF is used.

That way, people who have been using GIT_EXTERNAL_DIFF that is capable of comparing two directories do not have to change anything and can just give "--dirdiff" when they want to operate the command with this new mode of comparison. People whose GIT_EXTERNAL_DIFF is not capable of comparing two directories have two choices, but in either case they first would need to find an external tool they want to use with the "--dirdiff" mode. If they want to use the same new external tool for non "--dirdiff" mode, then they can set GIT_EXTERNAL_DIFF to it. If they want to keep using the command they have been using with GIT_EXTERNAL_DIFF when not in "--dirdiff" mode, however, they can keep their GIT_EXTERNAL_DIFF to the old "two files comparison" tool, and set GIT_EXTERNAL_TREEDIFF to the new one.

But that is all about envisioning how a proper integration of the feature in the main "diff/log -p" command codepath would work. I do not know if it is worth to add that to your script, which would be a stop-gap experiment until we find out if the "populate two temporary directories and have a tool compare them as a whole" mode is useful.