[LyX/master] Simplify checking whether files are controlled by SVN and GIT.

[Pavel Sanda]

On Thu, Dec 24, 2020 at 10:34:40AM -0500, Richard Kimberly Heck wrote:
> > I am sorry not to have a time to follow this thoroughly, but is this
> > cvs log / git log used only inh "register" case as initially discussed
> > or you want to use it on every file load?
> > Calling log could but pretty expensive operation for large archives.
> 
> The -n0 flag that Yuriy proposed should take care of that, too. So
> another reason to go that way.

I understood that. The minor concern was that it can still take seconds to get
the first commit touching particular file in larger git repos if its buried
down in the history.  But maybe it's not that different from git-ls.

My main concern though were changes to CVS - I haven't seen -n0 equivalent and
are you positive that cvs log does not actually try to connect to server (would
make us fail if you are offline)? It's really long time ago I used cvs, but
IIRC each tracked directory has the needed metadata locally at the place
so do we actualy need these changes to fulfil the users-list request?

Sorry for nitpicking, but given that this piece of code is executed at each
document load we better be super careful here...

Pavel