Re: master 4803fba487 1/2: 'C-x v v' on a diff buffer commits it as a patch (bug#52349)

[Dmitry Gutov <dgutov@yandex.ru>]

On 29.08.2022 19:46, Eli Zaretskii wrote:
> Why cannot this be implemented for every other VCS?

It can.

> Given diffs in a
> buffer, it should be as simple as running the Patch utility via
> shell-command-on-region, then committing the results.  Git has a
> special command for that, but we don't need a special command for
> other VCSes, if they don't have the equivalent of "git apply".  (I'm
> guessing that "git apply" simply runs Patch under the hood.)

No, 'git apply' puts the patch in a different place (index area), which 
means our implementation doesn't need to bother with moving all existing 
changes in the selected files somewhere else, then committing, and then 
restoring the previously-hidden changes.

The best way to implement the latter is not obvious to me. I suppose 
simply copying the files to /tmp and then overwriting them back at the 
end might do the trick, but can cause problems if the user edits the 
file buffer between creating the diff and finishing the checkin.

 > Can we please implement this for other VCSes as well?

Personally I hope we discover some popular extension to Mercurial which 
we'll be able to use in the same way as we do Git's index area here. And 
then say job well done and keep the less-popular and outdated backends 
unsupported.

'man hg' didn't give me enough clues, though.