checkheads: clarify that we no longer touch the head unknown locally
Since
c6cb21ddf74a, heads unknown locally no longer get any post processing
from obsolescence markers. We clarify this fact by only feeding the list of
locally known new heads to the function. This simplification of the input will
help moving that post-processing earlier in the function.
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.