shrink-revlog: instrument sort code to record statistics.
Notably, count "suboptimal" nodes (predecessor is not first parent)
and (with -v) report them at the end of the run.
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
See http://mercurial.selenic.com/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.