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

[Sean Whitton]

Hello,

On Fri 20 Sep 2024 at 05:08pm +01, Sean Whitton wrote:

> If you do C-c C-n in a diff-mode buffer with multiple hunks, a
> subsequent C-x v v signals a user-error from diff-file-next.  I think
> that the bug is in how diff-vc-deduce-fileset invokes diff-file-next.
> I'm not sure exactly how to rework diff-vc-deduce-fileset.
>
> It would be nice to fix this because then C-c C-n C-x v v would be a
> convenient way to commit just a single hunk.

I applied a brute force fix to diff-vc-deduce-fileset.
Attempting to commit a single hunk still fails because after C-c C-n the
file name header is not present, and 'git apply' can't handle a hunk
without a file name header.

We have diff-find-file-name to get the name; I wonder if we should try
to construct a fake file header?

-- 
Sean Whitton