hgweb: search() function supports direct pointing to revision This doesn't change the behavior, as queries directly pointing to revisions are not delegated to the search() function now.

hgweb: pass arguments which a function depends on explicitly in search This changes makes clearer which arguments can a function depend on. Now all the modified functions depend on the 'query' argument only, but future additions will change it.

hgweb: add dynamic search function selection, depending on the query This allows adding other specific search functions, in addition to current keyword search.

unionrevlog: extract 'baserevision' and 'baserevdiff' methods This makes possible to use unionrevlog class with subclasses of revlog that override revlog's 'revision' and 'revdiff' methods. In particular this change is necessary to implement manifest compression, as it allows extension to replace manifest class and override 'revision' amd 'revdiff' methods there.