hgweb: add a sendtemplate() helper function This pattern is common. Let's make a helper function to reduce boilerplate. We store the "global" template on the requestcontext instance and use it. The templater used by the helper function is the same templater that's passed in as an argument to the @webcommand functions. It needs to be this way because various commands are accessing and mutating the defaults on the templater instance. Differential Revision: https://phab.mercurial-scm.org/D2799

hgweb: use web.req instead of req.req We now have access to the modern request type on the requestcontext instance. Let's access it from there. While we're here, remove an unused argument from _search(). Differential Revision: https://phab.mercurial-scm.org/D2798

hgweb: stop setting headers on wsgirequest All commands now go through the new response API. This is dead code. Differential Revision: https://phab.mercurial-scm.org/D2797