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

[Sean Whitton]

Hello,

On Wed 09 Nov 2022 at 05:46PM GMT, Philip Kaludercic wrote:

> 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.

Typically you wouldn't want to format patches across a merge, so I would
suggest raising an error.

-- 
Sean Whitton