evolve: introduce a resolutionparent variable and store it in evolvestate This patch introduces a resolutionparent variable which will be the parent of final changeset after resolving content-divergent changesets. Till now, the parent is always the parent of one of the divergent node, but now in upcoming cases, it can be a successor of both the parents of divergent nodes.

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/