[RFC] Store old/new/mine versions of property conflicts

[Julian Foad <ju...@btopenworld.com>]

As a side-line to tree conflicts, I'm working on storing property
conflicts in a more machine-readable manner, storing the three
conflicting versions

  * "old" or "merge-left"
  * "new" or "merge-right"
  * "mine"

and providing API access to them so that a client can use them and not
have to rely on just the human-readable statements in the ".prej" file.

I didn't start by storing them, though; I started by writing an API for
retrieving them. (I haven't written any code for storing them, yet.)

Any comments on this would be appreciated. (I know a log message would
help you a lot. Sorry - later...)

(The patch is meant to be innocuous (not breaking existing code) but it
fails a few tests so there's at least one silly mistake in there.)

- Julian