commitctx: extract the function in a dedicated module the function have few callers (< 15) is quite long a mostly independent from the repository itself. It seems like a good candidate to reduce the bloatness of the localrepository class. Extracting it will help us cleaning the code up and splitting it into more reasonable-size function. We don't use a copy trick because the amount of code extract is quite small (<5%) and the de-indent means every single line change anyway. So this is not deemed valuable to do so. This is part of a larger refactoring/cleanup of the commitctx code to clarify and augment the logic gathering metadata useful for copy tracing. The current code is a tad too long and entangled to make such update easy. Differential Revision: https://phab.mercurial-scm.org/D8709

commitctx: document a fast path in _filecommit This block cut off a lot of logic, documenting the why and how seems useful to future reader. This is part of a larger refactoring/cleanup of the commitctx code to clarify and augment the logic gathering metadata useful for copy tracing. The current code is a tad too long and entangled to make such update easy. We start with easy and small cleanup. Differential Revision: https://phab.mercurial-scm.org/D8700

hgweb: simplify now that we always have a single path Both `templatedir()` and `web.templatepath` are now always a single path (or None). Differential Revision: https://phab.mercurial-scm.org/D8788

templater: simplify stylemap() now that templatedir() returns a single path Differential Revision: https://phab.mercurial-scm.org/D8787

templater: make templatepaths() return a single path, or None The function returns either a singleton list or an empty list, so it makes more sense to return a value or None. The plural in the name also doesn't make sense, but `templatepath()` is already taken, so I renamed it to `templatedir()` instead. Differential Revision: https://phab.mercurial-scm.org/D8786

templater: simplify templatepaths() to avoid iterating a singleton list The function iterates over a hard-coded list of one element since d844e220792a (templater: don't search randomly for templates - trust util.datapath, 2014-09-28). Differential Revision: https://phab.mercurial-scm.org/D8785