discovery: do not build sample if undecided is smaller than sample size This prevents crash with coming change in the mercurial discovery.

merge with stable

init: don't abort Mercurial on version mismatch Evolve causes Mercurial to exit if there is a version mismatch, even if no evolve command is invoked. This is a headache for people who have to work with multiple versions of Mercurial. Instead, raise an ImportError, which gives a warning but otherwise allows Mercurial to run non-evolve commands.