bug#2756: move SCCS later in vc-handled-backends

[Dan Nicolaescu]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

  > >> What problem?  And in what way is it a fix for it?
  > > The fact that SCCS generates unnecessary work for all files managed by
  > > bzr, git, hg (which is a good number nowadays).
  > 
  > Unnecessary work is not a problem in and of itself.

No, but given that it's unnecessary, and that it will be unnecessary in
the future too, why not get rid of it?

  > And, if this unnecessary work is a problem for Bzr, Git, or Hg files,
  > it's even more problematic for all the non-revision controlled files
  > which additionally need to do unnecessary work to determine that they're
  > neither under Git, Bzr, nor Hg control.  So changing the order won't
  > make much of a difference, other than hide the problem in the particular
  > case where you're lucky enough to access a file under the right VCS.

Yes, the thing is, what you are talking about above is a separate problem
that cannot be solved at this point.  
Even more, the solution for that problem would not solve the problem or
unnecessary checking for SCCS for systems that have sccs installed by
default (i.e. about all commercial unixes and free ones that install
cssc).  So why not just move SCCS to the end of the list?