Re: [PATCH 10/14] format-patch: add --range-diff option to embed diff in cover letter

[Junio C Hamano <gitster@pobox.com>]

Eric Sunshine <sunshine@sunshineco.com> writes:

> On Mon, Jul 23, 2018 at 12:28 PM Duy Nguyen <pclouds@gmail.com> wrote:
>> On Sun, Jul 22, 2018 at 11:58 AM Eric Sunshine <sunshine@sunshineco.com> wrote:
>> > diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
>> > index f8a061794d..e7f404be3d 100644
>> > --- a/Documentation/git-format-patch.txt
>> > +++ b/Documentation/git-format-patch.txt
>> > @@ -24,6 +24,7 @@ SYNOPSIS
>> >                    [--to=<email>] [--cc=<email>]
>> >                    [--[no-]cover-letter] [--quiet] [--notes[=<ref>]]
>> >                    [--interdiff=<previous>]
>> > +                  [--range-diff=<previous>]
>>
>> I wonder if people will use both --interdiff=<rev> and
>> --range-diff=<rev> often enough to justify a shortcut
>> "--all-kinds-of-diff=<rev>" so that we don't have to type <previous>
>> twice. But I guess we don't have to worry about this right now.
>
> My original thought was that --interdiff and --range-diff would be
> mutually exclusive, however, I quickly realized that some people might
> like to use both options together since each format has its strengths
> and weaknesses. (I've used both types of diffs together when preparing
> rerolls of my own series and found that, together, they provided a
> better picture of the reroll than either would have alone.)
>
> Based upon experience on this mailing list, I'd guess that most people
> would use only one or the other, though that doesn't speak for other
> projects. And, as you note, it's something that can be added later if
> warranted (plus, this series is already long and I'd like to avoid
> making it longer for something like this whose value is only
> speculative).

A few random thoughts.

 * I find it somewhat disturbing that use of dash is inconsistent
   between "--interdiff=<arg>" and "--range-diff=<arg>".

 * Perhaps "--interdiff=<previous> --range-diff" may be a possible
   way to say "use the same <previous> and show both"?  Do we want
   "--range-diff=<previous> --interdiff" to mean the same two
   meta-diff but shown in different order?

 * Do we expect that we may find a third-kind of "meta-diff" that
   sits next to interdiff and range-diff in the future?  I *think*
   two separate options "--interdiff=..." and "--range-diff=..." is
   still a good way forward, and we'd add "--frotzdiff=..." when
   such a third-kind of "meta-diff" turns out to be useful, without
   fearing proliferation of options, and that would be OK, but I am
   just thinking aloud to see if other people have better ideas.