[MERGE] 40% faster partial commits

[Ian Clatworthy]

Robert Collins wrote:
  :param: A container of paths.
>> I'd prefer "param paths: A container (non-None) of paths."
> 
> Sounds good, though the (non-None) is redundant - None is not a path.

Umm - I meant the container itself was non-None. I've move the
(non-None) before container to make that clearer.


>> If you're good with the above and want me to tweak and merge, let me
>> know.
> 
> Please do! I hope to be able to do this myself shortly, but I'd love to
> get this in.

Shall do. Lunch first though. :-)

Ian C.