evolve: check for None before adding in set of revisions to strip
After previous patch, replacements can contain None. Let's make sure we don't
add None to the revisions to strip during `hg evolve --abort`
The test changes demonstrate the usefulness of this and the previous patch. Now
abort is working and public changesets are not a problem.
syntax: re
/figures/[^/]+\.png$
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
^tests/.*\.err$
^tests/easy_run.sh$
^build/
^dist/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$
tests/\.testtimes
^docs/training/graphs/
^docs/training/html/
^docs/training/index.html
^docs/training/graphviz-images/
^docs/training/img/
^docs/training/output/
^docs/training/pandocfilters/