bug#57807: 29.0.50; Make vc-print-branch-log able to log multiple branches

[Juri Linkov]

>> Another variant is to bind 'C-x v c' to a command that uses
>> 'read-key-sequence' to read a key sequence from the vc keymap,
>> then call a command with call-interactively while let-binding
>> vc-want-edit-command-p, like project--switch-project-command does.
>> Then e.g. 'C-x v c L' will have mnemonic "vc command for root log".
>
> That seems alright.  Maybe we could use some symbol, e.g. '$' or '#',
> instead of a letter 'c', to distinguish its special status.

I see that 'c' might clash with a possible future command.
For example, git has a lot of commands whose names start
with the letter 'c': checkout, cherry-pick, clone, commit, ...
So the probability of the need to use 'c' is high.

OTOH, what key would keep the mnemonic of a prefix arg?
Maybe 'C-x v C-u'?