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 Wed 09 Nov 2022 at 08:28AM GMT, Philip Kaludercic wrote:
>
>> 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?
>
> I don't know, but the meaning of "the past N checked-in revisions of the
> whole tree" is what we need to agree upon, then it's just coding.

The critical edge-case here is what happens when branches are merged.
Do you pick a random branch or collect all the patches.  Or do you raise
an error, but then how do you detect that vc-generically.