Re: vc-state and unregistered

[Dmitry Gutov]

On 04/24/2016 03:11 PM, Michael Albinus wrote:

> > That could be fixed with using `none' instead, like `vc-backend'
> > does. Which I've mentioned already.
>
> That's the direction I have thought also. But in `vc-state' there is the
> following comment:

The comment is about the API and which value to return, not how the 
value is cached. My sentence, quoted above, was about how to cache it.

>   ;; Note: in Emacs 22 and older, return of nil meant the file was
>   ;; unregistered.  This is potentially a source of
>   ;; backward-compatibility bugs.

...and I have no idea how to interpret this comment. In Emacs 24, *and* 
in the upcoming 25.1, nil is *still* returned for unregistered files.

> Since I don't know why nil has been replaced by `unregistered', it might
> be a problem to use nil again as indication of unregistered files.

The salient question here is *in what way* has nil been replaced by 
`unregistered'.

> And
> we shouldn't change the interface wantonly, I believe.

The actual behavior will not change. This is what I'm proposing: to put 
the current behavior of (vc-state FILE) into spec.