bug#15698: Show commit revision

[Dmitry Gutov <dgutov@yandex.ru>]

On 24.01.2021 00:26, Lars Ingebrigtsen wrote:
>> Minor feature request. When committing from VC directory buffer, it
>> would be useful to see the exact revision number, because I usually
>> need it for reporting.  Currently my workflow is to commit =>
>> immediately open log buffer to see revision number.
>>
>> I'd suggest amending message "Checking in /home/user/dir...done" message as
>> something like "Checking in /home/user/dir...done as revision 1234".
> (I'm going through old bug reports that unfortunately got no response at
> the time.)
> 
> I'm not sure this would be generally useful -- particularly with VCs
> like git, where the revision string is really long, which means that you
> can't just type it from memory.

That sounds like a bit of a pain to implement, to be honest. If we 
wanted to show the revision at the end, and implement it in some 
backend-agnostic way, we'd have to add some new action, or an argument 
to vc-working-revision (like short-revision)... and implement that for 
some backends.

Further, while I also often use the resulting revision string, it really 
depends on whether I end up having to rebase before pushing, and that 
changes the revision.

>> Alternatively, just have VC directory buffer always show the last
>> revision (but this can be problematic/confusing for SVN at least,
>> e.g. my last commit was 7892, yet 'svn info' shows 7871).
> This could perhaps be useful, though?  That is, having a line in the
> -dir-extra-headers section saying what the current revision is?  I've
> added Dmitry to the CCs; perhaps he's got an opinion here.

This should be relatively easy to do, adding some text in each 
individual backends' function vc-XYZ-dir-extra-headers. Less 
indirection, too.

vc-git could show the short revision after the branch name, for example.

vc-svn could just add a new "extra header", I guess. Looks like its 
current list is much shorter.

I don't know what's the deal with SVN's revisions, though.