evolve: use registrar.revsetpredicate to register revset predicate functions
Now, using registrar.revsetpredicate of Mercurial directly in evolve
extension should be safe enough. because it has been available since
Mercurial 3.8, and minimum Mercurial version for evolve extension is
3.8, too.
#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()' 2>/dev/null \
> | xargs -0 flake8