context: add obsolete() method to basefilectx This method is now used in webutils.commonentry(), which adds common data items (commit hash, author, date, etc) for rendering changesets in hgweb. Usually, commonentry() is given a changectx as ctx; but in views related to files (e.g. file view, diff, annotate) it's replaced by a filectx, so the latter also needs to have obsolete() method.

check-code: grep's context flags don't need an extra space before number A bit of useless trivia found while researching this: OpenBSD's grep's -C has a default value (of 2) and disallows space before the argument (while -A and -B allow).