fold: allow operations on merge commits with some conditions
It's possible to fold revision chains that include a single merge commit: just
fold everything into the merge commit while saving its other parent (so it
continues being a merge commit). It's also possible to fold revisions that
include multiple merge commits, on the condition that they merge with not more
than 2 external changesets (i.e. a changesets that aren't going to be folded).
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/