histedit: adds hint how to reorder changesets at editor (issue3766)

revset: replace predicate by revsetpredicate of registrar To make all built-in predicates be known to hggettext, loading built-in predicates by loadpredicate() should be placed before fixing i18nfunctions but after all of predicate decorating.

revset: replace extpredicate by revsetpredicate of registrar This patch consists of changes below (these can't be applied separately). - replace revset.extpredicate by registrar.revsetpredicate in extensions - remove setup() on an instance named as revsetpredicate in uisetup()/extsetup() of each extensions registrar.revsetpredicate doesn't have setup() API. - put new entry for revsetpredicate into extraloaders in dispatch This causes implicit loading predicate functions at loading extension. This loading mechanism requires that an extension has an instance named as revsetpredicate, and this is reason why largefiles/__init__.py is also changed in this patch. Before this patch, test-revset.t tests that all decorated revset predicates are loaded by explicit setup() at once ("all or nothing"). Now, test-revset.t tests that any revset predicate isn't loaded at failure of loading extension, because loading itself is executed by dispatch and it can't be controlled on extension side.

registrar: define revsetpredicate to decorate revset predicate revsetpredicate is used to replace revset.predicate and revset.extpredicate in subsequent patches. This patch also adds loadpredicate() to revset, because this combination helps to figure out how the name of safe predicate is put into safesymbols. This patch still uses safesymbols set to examine whether the predicate corresponded to the 'name' is safe from DoS attack or not, because just setting func._safe property needs changes below for such examination. before: name in revset.safesymbols after: getattr(revset.symbols.get(name, None), '_safe', False) "automatic registration" described in help doc of revsetpredicate class will be achieved by the subsequent patch, which lists loadpredicate() up in dispatch.extraloaders.