Re: [Emacs-diffs] master de76a16: Performance improvements for vc-hg

[Daniel Colascione <dancol@dancol.org>]

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On 02/08/2016 11:55 AM, Stefan Monnier wrote:
>>>>>> "Daniel" == Daniel Colascione <dan.colascione@gmail.com> writes:

Huh. Where is that old email address coming from?

>>     Teach vc-hg how to read some Mercurial internal data structures,
>>     allowing us to avoid the need to run hg status -A, which is very slow
>>     for large repositories.  Fall back to running hg if anything looks
>>     funny.  vc-hg now puts the _working directory_ revision in the
>>     modeline instead of the file revision, which greatly improves
>>     performance and which allows us to again skip running hg in the case
>>     that we have an active bookmark.
> 
> Thanks Daniel.  Having written the same kind of thing for Bzr (tho it
> was much simpler in that case), and taking a step back, I think this
> reflects a mistake in VC: we probably just shouldn't provide such
> detailed info in the modeline, or at least not until the user makes
> explicit use of VC.
> 
> Having to go through the trouble of re-implementing part of the VCS to
> parse the internal data to figure out the working revision, even though
> we have no idea if the user will ever care, is deeply unsatisfactory.

I find the information useful, and we can now get it cheaply. Users can
easily remove vc-hg from vc-handled-backends if they don't want the
functionality.

What might be worthwhile is making it easier to use vc for a file if
that file's correct vc backend isn't vc-handled-backends --- that is, in
that mode, we'd initialize the vc goo only when the user asks for it. I
don't think that mode should be the default though.


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