refactoring and noting mv/rename after the fact

[John Yates]

One gripe I have with systems that claim that they support
versioning of mv/rename is that, unlike the other operations
I perform in my sandbox in which I use vc-unaware tools and
operate exactly as I would in any other portion of the file
system, I must remember that I am in a vc-controlled context
and use vc-aware mv/rename commands.  This is real a goatcha
when one is furiously refactoring.

I would like to suggest that when one commits a sandbox in
which both older files seem to have disappear and newer files
have appeared the vc-system should offer the user a chance to
identify delete/add pairs that actually represent mv/renames. 

To be friendly to both scripts and interactive users I would
suggest that the default should be the interactive prompting
but that there should be both a --no-prompt-for-mv-or-rename
and a --abort-if-possible-mv-or-rename flag.

I have a tougher time formulating a proposal for the logical
generalization, namely being able to call out when a newly
identified file did not spring into existence devoid of any
prior history, but instead was carved out of an earlier file.
But obviously I would love such functionality :-)

/john