bug#3641: Rename vc-dir-hide-up-to-date to vc-dir-toggle-up-to-date

[Dan Nicolaescu <dann@gnu.org>]

Bill Wohler <wohler@newt.com> writes:

>> From a usability point of view, a toggle makes sense here.
>
> I'm thinking my initial name isn't very good. It should certainly be
> vc-dir-toggle-something.
>
>> Just curious: Why does vc-dir-hide-up-to-date even exist if that's the
>> hard-coded behavior?
>
> Just answered my own question. If you check in one or more files, they
> will appear and be in the up-to-date state until you run x or g.

Right, so hiding the up to date entries is a matter of just looking at
the entry state and hiding it.
If vc-dir were to display all the up to date files, it would have to ask
the underlying VC system for the file list (or walk the directory tree
by itself...).  
Some VCS don't have a way to provide that.  For example it seems that
"bzr status" cannot do that.
Another problem is that on big trees it would take forever to get such a
file list.

Also after a VC operation vc-dir tries to update the state of all the
displayed items, if the list is too big, the display would take a long
time...

These are all potential problems, but what's missing is for someone to
implement the feature in at least one VC backend, play with it and tell
us how it works.