Hi Peff,

On Mon, 10 Sep 2018, Jeff King wrote:

> On Sun, Sep 09, 2018 at 07:19:51PM +0200, Ævar Arnfjörð Bjarmason wrote:
> 
> > >> And then I turn that into:
> > >>
> > >>     # @{u} because I happen to be on 'master' and it's shorter to type
> > >>     # than origin/master...
> > >>     git range-diff @{u} 38b5f0fe72...718fbdedbc
> > >
> > > I don't understand what you want with that @{u} or 'origin/master' in
> > > the first place.  It's unnecessary, the three-dot notation on its own
> > > works just fine.
> > 
> > Maybe I've been using the wrong mode all along, I passed over by habits
> > from tbdiff, which were surely copy/pasted from somewhere.
> > 
> > Looking at the git-range-diff manpage though it recommends <base> <rev1>
> > <rev2> over <rev1>...<rev2> when the topic has been rebased, which is
> > usually the case for e.g. a topic that's submitted to git.git (usually
> > be the time feedback has been gathered & a re-submission has been made
> > Junio has pushed another "master").
> > 
> > So isn't "<base> <rev1> <rev2>" the right thing to use over
> > "<rev1>...<rev2>" for git.git use? I think so, but I'm not sure.
> 
> The problem with <rev1>...<rev2> is that it finds the actual merge base,
> not the beginning of the topic.

That is actually not true, not for `range-diff`. If it sees `A...B`, it
will automatically generate `B..A A..B` from it.

That matters if the branches `A` and `B` have multiple merge bases.

> So if you have a 5-patch topic, but the first two patches weren't
> changed in the rebase, it won't show them at all!  I made this mistake
> in [1], for example.

Yep, that is very easy to do.

Another thing to note is that often `A...B` is not doing the right thing
with branches that go into `pu` because some of us contributors rebase
to `master` (or `next`) between iterations. For such a use case, I
myself prefer the `@{u}` version that Ævar wants to use. (Although I
leave off the three dots, in which case everything works quite
magically.)

> For a force-push, though, you may not care about seeing the topic as a
> whole, and that mid-topic merge-base could be just fine. So pasting just
> the "A...B" works.
> 
> I don't think your "@{u} A...B" makes any sense. You're giving _two_
> bases, which is weird. But even if you wanted to ignore the "..." base
> as a convenience to users of fetch, @{u} does not necessarily have
> anything to do with the @{upstream} of the topic at "A". You really want
> branch@{u}, which is on a separate part of the fetch output line (and
> your branch@{u} and the remote's are not necessarily the same, either;
> in this case you probably do not even have that branch checked out).

While `@{u}` in general does not relate to `A` nor `B`, it is quite
possible that it always does in Ævar's scenario. I would not want to
limit them in how they want to use Git from this point of view.

However, I would have a little bit of a problem with special-casing the
two-arg version when there are no dots in the first arg, and three dots
in the second one.

The problem here: the two-arg version already has a meaning: two commit
ranges. And it *is* conceivable that somebody wants to compare, say, the
full history of `git-gui.git` with a certain symmetric range in `pu`.
Granted, that is very obscure a use case, but it would be hard to
explain why the two-arg case refers to two commit ranges in some cases,
and in other cases not.

Ciao,
Dscho

> 
> -Peff
> 
> [1] https://public-inbox.org/git/20180821195102.GB859@sigill.intra.peff.net/
>