[MERGE] Improve tests for the behaviour of Tree.iter_changes for missing paths that are only present in one tree, and fix found bugs. (Robert Collins)

[Andrew Bennetts]

Robert Collins wrote:
> On Wed, 2008-08-13 at 09:17 -0500, John Arbash Meinel wrote:
[...]
> > 
> > BB:tweak
> > 
> > I agree with Andrew about raising TestNotApplicable, even though it
> > isn't your preference, it *is* the recommended way of doing it in the
> > test suite.
> 
> How about:
>  - I raise a bug saying that: our test parameterisation generates too
> many tests, we need a easy way of having some permutations getting
> opted-out (and that when that is done TNA gets deleted)
>  - I raise TNA

I'm ok with this course of action.  (Although I'm not at all sure that *all*
uses of TNA will be better if replaced with more complicated parameterisation,
I'm happy to explore the possibility.)

In the meantime, TNA is the best we've got (better than a bare return).

-Andrew.