hgweb: fix search {entries} to not return results of template expansion "{entries%changelogentry}" in raw/search.tmpl was utterly wrong because "{entries}" here was a generator yielding results of template expansion. That's why we have a weird hack in runmap(), which I'm going to get rid of. https://www.mercurial-scm.org/repo/hg/file/4.5.2/mercurial/templater.py#l469 We have two choices: a) drop "%changelogentry" from raw/search.tmpl b) fix "{entries}" to yield mappings I take (b) because that's what the other log-like "{entries}" do. The "entries" keyword is wrapped by mappinggenerator so "{entries}" without "%searchentry" still works.

templater: add class representing a nested mappings The mappinggenerator class is necessary to fix hgweb bugs without BC. The mappinglist is for nested formatter items. They are similar, so factored out the base class. The mappinglist could be implemented by using the mappinggenerator, but we'll probably need a direct access to the raw list, so they are implemented as separate classes. Note that tovalue() isn't conforming to the spec yet in that it may return a list of dicts containing unprintable resources. This problem will be fixed later. Tests will be added by subsequent patches.

templater: add function that expands internal literal templates This will be used when rendering nested formatter items with the default template, e.g. fm.nested('parents', tmpl='{rev}:{node|formatnode}', sep=' ') ^^^^^^^^^^^^^^^^^^^^^^^ the default item template

bookmarks: use isrevsymbol() for detecting collision with existing symbol Differential Revision: https://phab.mercurial-scm.org/D3167