cmdutil: use a generator expression instead of a list comprehension

cmdutil: rename template param to export to fntemplate It's actually a template for the filename, not a formatter template.

cmdutil: comprehensively document the interface of export I want to make some improvements here, but in order to make future patches easier to review I want to document the current state of the world.

tests: hide warning from test-xdg.t The test-xdg.t test uses the system hgrc because it unsets HGRCPATH. If the system has an extension enabled that doesn't work with the development version of Mercurial it prints an 'extension failed to load' warning. Let's just hide that by piping stderr to /dev/null.

policy: define C module versions individually This allows us to bump the version for a single module without changing all of them.

repoview: rename '_getdynamicblockers' to 'revealedrevs' (API) Recent mailing list discussion made me realised we could clarify these. We make the function "public" to encourage extensions to wrap it and we use a more explicit name that mirror "hideablerevs".

repoview: move '_getdynamicblock' next to 'hideablerevs' There are the two functions that extensions should use to augment the hidding logic. It seem better to have them together at the top of the file.

python3: allow hgloader to work with lazy loaders Don't clobber the loader returned from find_spec. This brings `hg version` down from 0.27 seconds to 0.17.

init: turn on demandimport for Python 3.6 and above This uses the new demandimport implementation for Python 3 introduced in previous patches. This doesn't yet enhance performance because it isn't integrated with the custom source file loader we use on Python 3. We'll integrate the two in upcoming patches.

demandimport: add python 3 implementation This implementation uses the new importlib finder/loader functionality available in Python 3.5 and up. # no-check-commit