tests: add test about aborting content-divergence when multiple parents This patch adds tests for --abort flag of hg evolve command when we are resolving content-divergence which are on different parents and parent of one of them is the gca of both of them. The tests shows that we are doing good and we should advertise the flag during conflicts.

#require test-repo pyflakes

Copied from Mercurial core (60ee2593a270)

  $ cd "`dirname "$TESTDIR"`"

run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)

  $ hg locate 'set:(**.py or grep("^#!.*python")) - removed()' 2>/dev/null \
  > | xargs pyflakes 2>/dev/null