topic: use registrar.revsetpredicate to register revset predicate functions Now, using registrar.revsetpredicate of Mercurial directly in topic extension should be safe enough. because it has been available since Mercurial 3.8, and minimum Mercurial version for topic extension is 4.0. This patch also removes modsetup() in topic/revset.py, because it is useless. BTW, this patch fixes an issue of "hg help revsets" output that custom revset predicates are not displayed as same as others, because they are not "inline literal" in reST syntax (``NAME``).

doc: make paragraphs before example code end with "::" for reST syntax This prevents lines in an example code from being treated as a part of normal paragraph. For issue example, lines are folded into one paragraph.