[MERGE] RevisionSpec.as_revision_id()

[Ian Clatworthy]

Aaron Bentley wrote:

> I've come up with a version I feel is much cleaner.
> 
> The key thing is does is make the partial_revision_history_cache the
> primary cache for format-6 branches.  This means that whenever there's a
> full-history cache, there's also a partial-history cache which contains
> the full history.  This removes the need for two codepaths-- branch6
> branches can use the partial cache always.
> 
> I've added _extend_partial_history, which extends the partial history,
> optionally stopping once it's reached a particular index.  This means
> that determining a previously-found revid is still done using [].index.
>  It also avoids doing more iteration, though frankly I don't think that
> would have a significant cost.

With John on holidays, thanks for taking this over.

bb:comment

I haven't reviewed the changes to revisionspec.py yet - I hope to do
that first thing tomorrow. The rest looks good except for the issue
Lukas has already raised - the changes in diff.spec_tree aren't quite
right. Needs a NEW entry as well.

Ian C.