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:

> Hello,
>
> On Tue 08 Nov 2022 at 08:31PM GMT, Philip Kaludercic wrote:
>
>> Sean Whitton <spwhitton@spwhitton.name> writes:
>>
>>>>> On the other hand, having a numeric prefix argument mean "send patches
>>>>> correspoding to the top N revisions of the current branch" would be very
>>>>> convenient.  Perhaps these two could be combined by using a negative
>>>>> number to mean also invert?
>>>>
>>>> This is the usual problem with numeric prefix arguments.  You don't get
>>>> that much expressivity with just an integer.
>>>>
>>>> That is why I would hesitate to assign any particular interpretation to
>>>> prefix arguments, before considering and weighing the options.
>>>
>>> Well, any other options in mind?  Varying the -N argument to
>>> git-format-patch/git-send-email is what I find myself using the most.
>>
>> The issue is finding a way for this to be expressed VC-generically.
>
> s/expressed/implemented/, right?

I meant expressed, but I don't remember what I meant ^^

So let's say implement.  What we could do is just call
`previous-revision' for the backend N times, but with what file?