Re: master 101f3cf5b9: Add support for user edits to VC command arguments

[Juri Linkov]

>>>>>     Sean> +(defvar vc-want-edit-command-p nil
>>>>>     Sean> +  "If non-nil, let user edit the VC shell command before 
>>>>> running it.")
>>>>
>>>> BTW, `-p` stands for "predicate", IOW *functions* that return booleans.
>>>
>>> I thought that in Lisp we often call boolean values predicates too, even
>>> though that violates the usage of 'predicate' in mathematics.
>>>
>>> Is there some other convention for booleans like this one?
>>
>> Usually we don't need it because the name says it, like
>> `vc-let-user-edit-commands`.
>
> I'd be happy to change it to this (minus the plural) if you and/or
> others would like.

Why not plural?  Some vc commands run several shell commands.
For example, 'vc-git-log-incoming' runs two shell commands:

  (vc-git-command "fetch" ...
  (vc-git-command "log" ...

We need first to try this feature for more vc commands to see
if some filtering is needed to not edit secondary shell commands,
and then maybe allow customization via regexps or symbol properties
which commands need editing in case of multiple shell commands.