tests: reduce dependence on previous tests for setup The tests in test-evolve-phase-divergence.t built on each other for no good reason, which makes the tests hard to modify and hard to read. This patch cleans up some of them. We should clean up the rest too, but the rest won't matter for my next patch, so I haven't bothered.

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