bug#68183: 28.3; vc-dir fails when I have a certain branch checked out

[Kévin Le Gouguec]

Dmitry Gutov <dmitry@gutov.dev> writes:

> Sorry about the late reply.

(Not at all, thanks for taking a look 🙏)

>> FWIW, the current patch will show
>>      Branch     : vc-dir-tracking-branch
>>      Tracking   : origin/master
>>      Remote     :https://git.savannah.gnu.org/git/emacs.git
>> for my checkout of this work-in-progress patch, and
>>      Branch     : vc-dir-bug
>>      Tracking   : master
>>      Remote     : none (tracking local branch)
>> for a checkout made following Tom's recipe, and
>>      Branch     : trunk
>> for a fresh 'git init' with just a default branch.
>
> IIUC you're adding the new "Tracking" header to the output? That seems like 
> it should be helpful.
>
> Is there a way that we could/should optimize the display? I.e., I guess the 
> most common case will be something like:
>
>       Branch     : foo-bar
>       Tracking   : origin/foo-bar

Right, the current patch indeed shows this for a common-case clone of
the Emacs repo:

    VC backend : Git
    Working dir: ~/src/emacs/master/
    Branch     : master
    Tracking   : origin/master
    Remote     : https://git.savannah.gnu.org/git/emacs.git

> which is not bad, but might be less useful than indicating that the current 
> branch does not track anything (and so the next 'git push' should come with 
> '-u'), or tracks a differently named branch. It might be more ergonomic to 
> emphasize "irregular" scenarios and maybe even save on the extra line in the 
> "common" one.

Good food for thought.

Re. optimizing the display (which I interpret as reducing redundant
information): as someone who often works with multiple remotes, seeing
"Branch: FOO ; Tracking: origin/FOO" is actually useful, so I wouldn't
want to remove the "tracking" bit unconditionally.  OTOH it could surely
be condensed to a single line, say

    Branch     : master (tracking: origin/master)

Likewise, in the local-tracking-branch case, we could go from

    Branch:    : vc-dir-bug
    Tracking   : master
    Remote     : none (tracking local branch)

to just

    Branch:    : vc-dir-bug (tracking: local master)

Re. emphasizing irregular scenarios, specifically those where 'git push'
will require '-u': I like the idea, but I am wary of us getting lost in
the weeds second-guessing Git's intentions.  E.g. even when
branch.foo.merge and branch.foo.remote are unset, 'git push' can still
be called without '-u' if push.default is 'current' and
remote.pushDefault is set (whereas 'git pull' will fail).

> Just a thought. Not something that needs to be addressed right now. And I 
> might as well be off the mark here.

I agree it's worth thinking about.  The Right Solution™ would probably
come with user options to let users fine-tune which details they care
about?  It would be interesting to survey Git UIs to see how they
approach this (FWIW I am partial to Magit's presentation, but I have not
studied how it handles all the corner cases we considered).

>>> * maybe the new header deserves a NEWS entry.
>> Maybe?
>
> It wouldn't hurt. Up to you.
>
> Anyway, I think the patch is good to go. Please feel free to install it; 
> whatever cosmetic changes we might like to add could be done later.

ACK.  I might go a head and install then (after polishing the changelog,
i.e. re-filling and scrubbing Unicode ellipses) in the spirit of getting
the original issue fixed; perhaps worth holding off on the NEWS entry
until we decide how exactly things should look.