rank: add test with golden values
This adds a regression test for the computation of the rank, using the current
values computed with the naive algorithm as the "golden" reference.
Differential Revision: https://phab.mercurial-scm.org/D12142
#require black test-repo
Black needs the real USERPROFILE in order to run on Windows
#if msys
$ USERPROFILE="$REALUSERPROFILE"
$ export USERPROFILE
#endif
$ cd $RUNTESTDIR/..
$ black --check --diff `hg files 'set:(**.py + grep("^#!.*python")) - mercurial/thirdparty/**'`