bug#58383: 29.0.50; Make it easier to invert vc-prepare-patches-separately

[Philip Kaludercic <philipk@posteo.net>]

Sean Whitton <spwhitton@spwhitton.name> writes:

>>> Typically you wouldn't want to format patches across a merge, so I would
>>> suggest raising an error.
>>
>> And this is something I don't think can be /expressed/ using vc, because
>> while I can collect a number of revisions using `previous-revision',
>> there is no general way to verify if a commit is a merge commit.
>
> Can we do that part on a VCS-by-VCS basis?  Default to just calling
> previous-revision and hoping for the best, but giving vc-git.el a chance
> to raise an error.

I guess that would be possible, though it will probably require a new
VC method :/  The new `prepare-patch' takes a revision, so it doesn't
make sense to pass it a number and have it return multiple patches.

Perhaps it will be easier/cleaner to just accept that avoiding merge
revisions is the users responsibility.

But just to have mentioned it:  Do you know that you can mark revisions
in log-view and then vc-prepare-patches will use these as the default
input when prompting for revisions?