[MERGE] special case the no-args version of revision-info

[Robert Collins]

Robert Collins has voted reject.
Status is now: Vetoed
Comment:
yeah, this is a cute but basically wrong approach, its code that we 
don't need.

I'd approve a fix to the revision spec to special case -1 though :), as 
that has the benefit that it is in the correct location for maintainers 
to see.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C47D9A4DA.4070304%40canonical.com%3E