[MERGE] Add optional 'fetch_spec' to argument to Repository.fetch

[Andrew Bennetts]

Robert Collins wrote:
[...]
> remove the knit XXX: its not going to be found there :)

Done.

> MiniSearchResult needs a couple of nominal tests.

Ok, I've added a basic test.

> Please add to the docstring of Repository.fetch that fetch_spec can  
> handle multiple heads.

Done.

> We need a test_smart test for using MiniSearchResult I feel.

Fair enough.  Done.

> I'd like to suggest deprecating revision_id, but I think that needs a  
> [more] complex search result to be able to pass in, so we should wait.

I agree.

> Perhaps MiniSearchResult could take a list of revs rather than just one,  
> as a heads-list.

Yeah.  I originally had that, but then I simplified, probably too much.  I've
now adjusted it to take a heads list.

> Also, perhaps MiniSearchResult should be a PendingAncestryOfResult ? (Or  
> similar name; Mini is just too vague/contextual.

It's now PendingAncestryResult, and has a docstring, so that helps too :)

Thanks very much for the review.

-Andrew.