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.

chgserver: check type passed to S channel It currently only supports the "system" type. Add an explicit check.

chg: send type information via S channel (BC) Previously S channel is only used to send system commands. It will also be used to send pager commands. So add a type parameter. This breaks older chg clients. But chg and hg should always come from a single commit and be packed into a single package. Supporting running inconsistent versions of chg and hg seems to be unnecessarily complicated with little benefit. So just make the change and assume people won't use inconsistent chg with hg.

rebase: fail-fast the pull if working dir is not clean (BC) Refuse to run 'hg pull --rebase' if there are uncommitted changes: so that instead of going ahead with fetching changes and then suddenly aborting the rebase, we can warn user of uncommitted changes (or unclean repo state) right up front. In tests, we create a 'histedit' session to verify that also an unfinished state is detected and handled.

commit: fix unmodified message detection for the "--- >8 ----" magic We need the raw editortext to be compared with the templatetext.

commit: update test to actually modify template text We have a check for unmodified commit message (introduced by bec1a579ebc4), which should be enabled for the "--- >8 ---" magic but currently not.

pager: wrap ui._runpager As discussed at [1], ui._runpager will be the new low-level API accepting a pager command to actually run the pager. And ui.pager is the high-level API which reads config directly from self. This change is necessary for chgserver to override _runpager cleanly. [1]: www.mercurial-scm.org/pipermail/mercurial-devel/2016-December/091656.html

summary: use ui.label and join to write evolution troubles Follow-up on 7b526670f540 to avoid a convoluted loop.

log: drop unnecessary ui.note label from "trouble: " line Follow-up on f05ede08dcf7 and 6d0b1a69f98c.