bug#7675: 24.0.50; vc-checkin should prompt if the fileset changes

[Bob Rogers]

   From: Stefan Monnier <monnier@iro.umontreal.ca>
   Date: Sun, 19 Dec 2010 08:57:00 -0500

   Thanks for submitting a patch to try and fix this problem.
   A quick obvious issue, tho:

   > --- a/lisp/vc/vc.el
   > +++ b/lisp/vc/vc.el
   [...]
   > +(defun log-edit-deduce-fileset (state-model-only-files)

   If it's in vc.el it can't start with the "log-edit-" prefix.

Yes, I was wondering about that.  I had thought about putting it in
log-edit.el, but it seems closer to VC internals than log-edit
internals.  Which would you prefer:  Rename it, or move it?  If
"rename", would "vc-log-edit-deduce-fileset" suffice?

           Stefan "who hasn't yet had time to look at the rest of the patch"

Just as well, considering that the patch fails for single-file commits.
I am thinking that vc-commit only ever needs to re-examine the fileset
if the commit was (a) started in *vc-dir* and (b) with marked files.
Otherwise, the fileset is determined by the way C-x v v is invoked, and
there's no way to change it later.  True?

   And while I'm thinking of it, a VC fileset really ought to be
represented by a struct, since all this car-ing and cdr-ing is really
messy.  But filesets are passed to backends, so testing such a change
would be a pain.  What are your thoughts?  It is worth it?

                                        -- Bob