phabricator: add tests of templatekeyword Having tests is paying off: I found a bug and now it'll be easy to fix! Differential Revision: https://phab.mercurial-scm.org/D4603

phabricator: move extension from contrib to hgext It's well-enough tested now and widely enough used I think we should ship it. Differential Revision: https://phab.mercurial-scm.org/D4602

tests: add some basic tests of phabricator interactions This uses the vcr library to avoid hitting phabricator on every test execution. In order to generate new recordings (vcr calls them cassettes) just remove the appropriate json file, and the test will regenerate it. It's not my favorite way to test things, but it'll let us have test coverage on the phabricator extension that'll make it resilient to refactors in core and let us move it to hgext. In the future, it'd probably be better to have a docker container we can spin up for creating the vcr recordings, but for now this is enough better than nothing I'm going to declare victory. Coverage reports about 73% of the extension is now covered. Differential Revision: https://phab.mercurial-scm.org/D4601

phabricator: add support for using the vcr library to mock interactions I'll use this in an upcoming test. The decorator dancing in this is more complicated than I'd like, but it beats repeating all this code everywhere. Differential Revision: https://phab.mercurial-scm.org/D4600

keepalive: work around slight deficiency in vcr VCR's response type doesn't define the will_close attribute. Let's just have keepalive default to closing the socket if the will_close attribute is missing. Differential Revision: https://phab.mercurial-scm.org/D4599

hghave: add a checker for the vcr HTTP record/replay library I'm going to use this to write some tests of the phabricator extension. Differential Revision: https://phab.mercurial-scm.org/D4598