evolve: handle case when newnode can be None while continuing evolve There can be case when `hg evolve --continue` is run, when working directory is clean and there is nothing to be included in the new commit. Let's make sure we handle such cases correctly and obsolete the node which is evolved with parent of wdir as successor. This is same as what rebase does.

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/