bug#38044: 27.0.50; There should be an easier way to look at a specific vc commit

[Dmitry Gutov <dgutov@yandex.ru>]

On 20.11.2019 18:34, Eli Zaretskii wrote:

>> How would that even work? vc-diff will always delegate to vc-git-diff.
> 
> It will work if we program either vc-diff or vc-git-diff to call "git
> show" under some specific circumstances.

That makes little sense to me, sorry.

>>>> IMO the log message is more important because it describes and justifies
>>>> what happened. Showing the diff is good as well.
>>>
>>> That's not relevant to the issue at hand.  Like it or not, VCSes other
>>> than Git describe a revision by the diffs alone.
>>
>> It's 100% relevant, and the fact that certain older VCSes can't do this
>> should have no bearing on whether we implement a satisfactory UI in VC
>> or not. That's the whole purpose of VC: make interacting with different
>> VS systems easier.
> 
> Easier, yes.  But also present the results in a familiar enough form.
> If users are accustomed to seeing a revision described by diffs, then
> this is what they should by default see in VC, IMO.

There's nothing unfamiliar about also seeing the author name and the 
commit message.

Also: most of our users are Git users. Hence, users are accustomed to 
'git show'.

>>>> Maybe the other VCSes don't have a simple command to do the same, but
>>>> they can either be called twice, or use special formatting. For
>>>> instance, Hg can use this command:
>>>>
>>>> hg log -r <REV> -p
>>>
>>> IMO, this is over-engineering.  If the VCS developers don't see the
>>> need to have a commands which shows meta-data together with the diffs,
>>> we should not force that on that VCS.
>>
>> They added the '-p' flag. So apparently they did see the need.
> 
> Then maybe the hg back-end should indeed call "log -r -p", if that's
> what hg users are used to (I don't use hg).  What I mean is that we
> should show a revision like users are accustomed to see it with the
> particular back-end; jumping through hoops to produce Git-like display
> where users don't really expect it is IMO over-engineering.

I disagree. I think the possible arguments are exhausted at this point.

Are you going to invoke the privilege of the Emacs maintainer? All I got 
to say to this is "lisp/vc/*" is near my name in admin/MAINTAINERS.

> And I'm also saying that conceptually a revision's description is a
> kind of "diff" operation, so it should preferably be a sub-command of
> "C-x v =".

That's not how I think about it either. Again: I think the metadata is 
just as important. And we can't get to that metadata from the diff output.