evolve: add test to demonstrate a bug when active topic is empty
Added test shows that when current active topic is empty and we try
to run `hg up`, it fails with an error. It's because this case is not
correctly handled when we find a destination to update (when topics
are in play)
Next patch will fix this.
#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