Re: Feature request: be able to pass arguments to difftool command

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 28, 2018, 19:37 UTC
Message-ID: <xmqqpny2ffjv.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20180828175711.3a0aeacc@pc09.procura.nl>

"H.Merijn Brand" <h.m.brand@xs4all.nl> writes:

Show 6 quoted lines

> So, my wish would be to have an option, possibly using -- to pass
> additional command line arguments to git difftool, so that
>
>  $ git difftool $commit~1..$commit -- -m -v2
>
> would pass the arguments after -- transparantly to ccdiff (in my case)

At the syntax level passing any option after "--" would be a no starter, as I would imagine that "git difftool $revs -- $paths" should still be supported.

At the concept level, however, I can see why such a feature would be useful. Perhaps

    $ git difftool --backend-option=-m --backend-option=-v2 HEAD
    $ git mergetool --backend-option=--foo

with appropriate way(s) [*1*] to make it easier to type (and implement) would be an acceptable avenue to pursue, I wonder?

[Footnote]

*1* There are various possible ways, not all of them are mutually
    incompatible.

    a. Give a short-form synonym, e.g. -X, to "--backend-option";

    b. Assume that backend option always begins with a dash and add
       one when missing, e.g. -Xm becomes --backend-option=-m

    c. Allow giving multiple backend options on a single option and
       split at whitespace, e.g. --backend-option="-m -v2"

    d. Allow difftool.$toolname.opts configuration variable that is
       multi-valued, so you can say

	git -c difftool.ccdiff.opts=-v2 -c difftool.ccdiff.opts=-m difftool

       (of course, not necessarily from the command line but the
       point is you could configure it)

    Some of these (e.g. b, c) may not be desirable, though.