On 11/11/2023 10:03 PM, Eli Zaretskii wrote:
>> Date: Sun, 12 Nov 2023 00:00:13 +0200
>> Cc: 67062@debbugs.gnu.org
>> From: Dmitry Gutov <dmitry@gutov.dev>
>>
>> Our general approach is to prefer global options and dynamic dispatch on
>> backends, resorting to using per-backend options when it's much easier
>> to do.
> 
> Which I think is the case here.  What other VC backend has such long
> revision strings?  I couldn't think of any.

Game of Trees[1] is one, though you could argue that that's cheating 
because it uses the Git repository format. It does have a GNU ELPA 
package though, so the author would probably want to add a 
'vc-got-short-revision' function. (Or something similar depending on 
what this patch looks like if/when it merges.) Looking at some GoT 
repositories, they *do* still use the long SHA-1 hashes for revision 
identifiers.

In fact, there are at least a couple Git-compatible VCSes now. Facebook 
wrote one called "Sapling", though I haven't used it. Based on some 
screenshots at least, it looks like Sapling also uses SHA-1 hashes for 
revision IDs.

In any case, we don't necessarily need to provide a default 
implementation for the 'short-revision' function. What about something 
like this? I'm not sure it's better, but it does let us avoid defining a 
no-op implementation for the "default backend".

[1] https://gameoftrees.org/index.html

[2] https://github.com/facebook/sapling