bug#12492: 24.2.50; Open vc-dir buffer easier and faster

[Dmitry Gutov]

Tags: patch

Two changes:
1) All version controlled buffers have after-save-hook set up to call 
vc-dir-resynch-file. So if we're just bringing up a buried vc-dir 
buffer, we (almost?) never need to refresh it. This cuts about 1 second 
or more on my machine, depending on the backend.
2) For almost all backends we can easily deduce the repository root 
directory (exceptions: cvs, rcs, sccs), and I believe that in almost all 
cases the user wants to see the status of this directory, not of some 
subdirectory or any directory unrelated to the current buffer.
Hence the function vc-root-dir, which I think should be bound to 'C-x v 
d' and the respective menu item.
In the rare case when the user need to do something unusual, they can do 
M-x vc-dir.
When the backend doesn't have the function vc-xx-root, vc-root-dir 
interactively delegates to vc-dir, so for CVS, for example, the behavior 
will not change.

vc-dir.diff
Description: Text document