Re: Introducing 'unrecognized and 'ignored

[Alexandru Harsanyi <harsanyi@mac.com>]

On 29 Dec 2007, at 2:45 AM, Eric S. Raymond wrote:

> I've spent the last couple of hours looking at this issue.
> A reminder: the payoff for getting it right would be another
> significant speedup in (vc-dired-hook), which would translate to
> a faster C-x v d display.
>
> Remarkably, it looks as if the code does not actually depend
> in any significant way on the nil return from (vc-state file) meaning
> that FILE is unregistered.  Tests that might have used this method
> use vc-backend instead.  So introducing an 'unregistered state
> shouldn't actually break anything.
>
> Alex Harsanyi: A cvs-ignorable-file-p would actually be useful, if
> you're still interested. Under later systems it's faster to get this
> by doing a bit of estra parsing of rge status report.
>

I had a look at the problem last night and wrote the code to load a  
cvsignore file and produce a regexp to match the ignored files,  
however the whole mechanism required by `vc-BACKEND-ignorable-file-p'  
is quite tricky to implement corectly (in a way that both Emacs and  
the backend agree 100% on what files are ignored).  Here are two of  
the problems I found when I looked at an implementation for CVS:

  * CVS will ignore a file only if it is unregistered.  For  
example .o files are ignored from a CVS status listing, but if an .o  
file is registered than that file will show up in the listing.  This  
requires checking whether a file is registered or not, a thing which  
we try to avoid.

  * There's a 'per-repository' cvsignore file at $CVSROOT/CVSROOT/ 
cvsignore which Emacs cannot access directly for remote repositories.


With extended vc-state states I don't think there is a need for `vc- 
ignorable-file-p' at all:  `vc-BACKEND-dir-state' should set the  
state for each registered file and for files it can register.  `vc- 
dired-hook' can than simply look for the vc-state property and if it  
is missing it can assume that the file is ignored.

Best Regards,
Alex.