stack: fix phasecache._phasesets check logic When _phasesets is not None, it's a list, and it contains set()s of revisions in a specific phase, starting from public, draft, secret and so on. But since repos are supposed to have the majority of revisions in public phase, the first element of this list is not a (potentially huge) set, but None. Previously this code tried to check if there's any element that is None, and was always finding None at index 0, so the short path was executed every time and the rest of the function was never used.

#require test-repo

  $ checkflake8() {
  >   if ! (which flake8 > /dev/null); then
  >     echo skipped: missing tool: flake8;
  >     exit 80;
  >   fi;
  > };
  $ checkflake8

Copied from Mercurial core (60ee2593a270)

  $ cd "`dirname "$TESTDIR"`"

run flake8 if it exists; if it doesn't, then just skip

  $ hg files -0 'set:(**.py or grep("^#!.*python")) - removed()' \
  > -X hgext3rd/evolve/thirdparty \
  > 2>/dev/null \
  > | xargs -0 flake8