We add a -R/--repo option to run the benchmarks on another repository. This is
very useful as some repository are bigger/more interesting than the mercurial one.
Before this changeset, you had to stand in the root of the mercurial repo to run
the `revsetbenchmark.py` script. Otherwise, the perf extension would not be
found a `./contrib/perf.py` and the script would crash in panic.
We now figure out the contrib directory from the location of this script. This
makes it possible to run the script from other location that the mercurial repo
root (but you still need to be in the core mercurial repository)
The script is now in python. That translation is very raw, more improvement to
comes:
The "current code" and "base" entry have been dropped. This is trivial to get
same result using a tagged revision or "." in the list of benchmarked revision.