help: merge the various operator sections of revsets, filesets and templates Having sections for specific operator types assumes the user already knows what type of operators are supported. By having a common heading, the user can simply lookup help for "(revsets|filesets|templates).operators".

help: apply the section headings from revsets to templates Unlike filesets, there are a few distinct headings that are not shared with revsets. But common names are used where possible.

help: apply the section headings from revsets to filesets This has the nice property of visually breaking up the wall of text. It also allows specific smaller sections to be called out. For example, `hg help filesets.predicates` now prints just the predicate section. At the moment, the revset headings are a superset of the fileset headings, so there is consistency in how example, predicate and operator help is called out. The reference to `hg help patterns` was moved to the overview section, so that it isn't stuck in the examples section.

chg: check type read from S channel The previous patch added the check server-side. This patch added it client-side.