Re: VC and bzr.

[Eli Zaretskii <eliz@gnu.org>]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Date: Fri, 23 Apr 2010 04:18:09 +0200
> 
> Oh, and I think that support for asyncrhonous commits on VC is good to
> have, but with bzr sometimes taking *minutes* for a commit, special
> situations must be considered, like the user editing and saving files
> while the commit is on the way, or trying to commit something while the
> previous one is not finished yet. It is not unlikely that some of those
> scenarios may end with some breakage.

It is broken already.  As long as bzr is running, it locks the
.bzr/checkout/dirstate file, and visiting any file under bzr during
this time displays an error message because "bzr status" barfs due to
the locking.  This is for some reason more grave on MS-Windows,
probably because the way bzr opens files doesn't allow for sharing
with other programs.

And, btw, the speed of bzr operations doesn't matter much, because
even seconds would cause these problems with a significant
probability.

IOW, maybe bzr is good enough to use for Emacs development, but not
yet good enough to use it from within Emacs.  Someone should break the
news to Bazaar developers.

Until and unless this is fixed, I think we should stop using "bzr
status" for accessing VC-related information when we do file I/O.  We
should implement some other way of accessing that info, that doesn't
involve running bzr on each file op.  Or maybe we should access it
lazily (it's not that seeing the up-to-date revno in the mode line is
such a crucial feature), or somehow access it en masse, then cache it.