manifestmerge: use already existing fl2 synonym for m2.flags(f) Probably not a noticeable performance gain, but shortens the code slightly.

merge: drop underscore prefix from _checkunknown() The method has been called from commands.py since 3eab42088be4 (update: just merge unknown file collisions, 2012-02-09), so drop the underscore prefix that suggests that it's private.