revlog: speed up prefix matching against nodes
The radix tree already contains all the information we need to
determine whether a short string is an unambiguous node identifier.
We now make use of this information.
In a kernel tree, this improves the performance of
"hg log -q -r
24bf01de75" from 0.27 seconds to 0.06.
revset: add function for matching extra data (
issue2767)