bug#73387: 30.0.90; C-x v v in diff-mode doesn't work after C-c C-n

[Dmitry Gutov <dgutov@yandex.ru>]

On 25/09/2024 09:34, Sean Whitton wrote:
> On Tue 24 Sep 2024 at 08:36pm +03, Dmitry Gutov wrote:
> 
>> OTOH, maybe what you want to do here could be reached some other way -
>> e.g. instead of 'C-x n n' we would have a command which edits the diff buffer
>> to leave in only the hunks intersecting the current region. When the
>> subsequent (buffer-string) would do the right thing.
>>
>> The latter might also be a better fit for the overall workflow we were
>> thinking about (create a diff -> alter it as necessary -> commit).
> Yeah, I already wrote something like that for my init.el.  I would like
> to find some way to combine it with the existing C-c C-n, if we can.
> 
> Maybe:
> if (equal (diff-bounds-of-hunk) (list (point-min) (point-max)),
> then C-x v v prompts, "Kill all hunks but this one and commit? (y/n)" ?
> 
> Else if the buffer is narrowed, C-x v v signals a user-error that it
> can't handle arbitrary narrowings.
> 
> Then it's just C-c C-n C-x v v but you're asked to confirm before all
> the killing occurs, just in case.

Suppose C-c C-n (or probably a different but similar binding) edited the 
diff instead of applying the narrowing, in a way that retained the file 
header(s), but keeping only the hunks intersecting the region or just 
the current one.

Would that work for you just as well, or do you prefer to use narrowing 
anyway, for some other reasons?