Re: moving SCCS later in vc-handled-backends

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> When opening any version controlled file that is under one of the more
>> modern VCs, SCCS is tried first.
>> Given that it's not a popular system, this is pure overhead,
>> so it would be better move it at the end of vc-handled-backends.
>> Any objection to this change:

> Yes.  This change is backward incompatible and buggy; the rationale
> for SCCS being in the "early" group still holds as far as I know,
> unless SCCS has improved its support for whole-tree commits recently.

100% agreement.  For any non-VC files, the whole list will be traversed
anyway, so the order doesn't make much difference (if any) in terms
of performance.  If we change ordering, it should not be for
performance reasons (unless you can actually show some hard-data
demonstrating the positive effects in realistic scenarios).

We could consider removing elements from the list based on the
presence/absence of the necessary tools on the system (tho it might not
be such a great idea either, since for many backends, the tools are not
necessary to find the backend and the current revision and state, and
also because many backends can be used via Tramp).


        Stefan