Fix hg logging commands.
The commands used in extract_summary and extract_description weren't quite

right.
To start with, the two revisions were in the wrong order. Back when it used the

revision order (r1:r2), it would at least give some results, but the change to

using the DAG range (r1::r2) made it return nothing for the description.

Switching the order of the revisions fixed it.
Once the revisions were switched, the order of items in the log was backwards.

I've changed it to use reverse(r1::r2) to get the right ones.

Posted changes with hg using both the current branch and revision ranges. Saw

the right summaries and descriptions.