revsets: define a none() revset This can be useful for default values in corp-wide configuration (e.g. for commits to hide, which defaults to none()), and perhaps in scripts. I named it none() rather than empty() to match all(). Differential Revision: https://phab.mercurial-scm.org/D3713

statprof: fix save and load Fix these functions even if they don't are used at the moment. Thanks to Yuya Nishihara for spotting that.

perftemplating: abort on incompatible version This is what the other debug commands do. Thanks to Yuya Nishihara for pointing this out.