py3: use startswith() to check existence of trailing '\n' in .hgtags file

py3: silence return value of file.write() in test-command-template.t

error: fix isinstnace check to use bytes instead of str Differential Revision: https://phab.mercurial-scm.org/D2528

py3: whitelist another nine passing tests I now see 347 tests passing[0] and 336 failing, so we're past halfway there. Hooray! 0: A few tests appear to regress in small ways (doctest output changes, for example) on Python 3.7.0a1, which is what I'm now using to test. That said, I'm pleased to report no major regressions. Differential Revision: https://phab.mercurial-scm.org/D2439

util: use pycompat.bytestr() on repr() in date parse abort Avoids the b'' prefix. Differential Revision: https://phab.mercurial-scm.org/D2438

py3: whitelist 14 new tests passing 12 new tests passed because of parent changeset and 2 were passing before that too. Differential Revision: https://phab.mercurial-scm.org/D2523

py3: slice over bytes to prevent getting ascii values This fixed reading of mergestate files and fixes 14 tests on Python 3. Differential Revision: https://phab.mercurial-scm.org/D2522

wireprotoserver: move SSHV1 and SSHV2 constants to wireprototypes To avoid a cycle between modules in an upcoming commit. Differential Revision: https://phab.mercurial-scm.org/D2482

wireproto: use named arguments for commandentry We'll be adding more arguments in upcoming commits. Using named arguments will make the code easier to read. Differential Revision: https://phab.mercurial-scm.org/D2481

debugcommands: support for triggering push protocol The mechanism for pushing to a remote is a bit more complicated than other commands. On SSH, we wait for a positive reply from the server before we start sending the bundle payload. This commit adds a mechanism to the "command" action in `hg debugwireproto` to trigger the "push protocol" and to specify a file whose contents should be submitted as the command payload. With this new feature, we implement a handful of tests for the "unbundle" command. We try to cover various server failures and hook/output scenarios so protocol behavior is as comprehensively tested as possible. Even with so much test output, we only cover bundle1 with Python hooks. There's still a lot of test coverage that needs to be implemented. But this is certainly a good start. Because there are so many new tests, we split these tests into their own test file. In order to make output deterministic, we need to disable the doublepipe primitive. We add an option to `hg debugwireproto` to do that. Because something in the bowels of the peer does a read of stderr, we still capture read I/O from stderr. So there is test coverage of what the server emits. The tests around I/O capture some wonkiness. For example, interleaved ui.write() and ui.write_err() calls are emitted in order. However, (presumably due to buffering), print() to sys.stdout and sys.stderr aren't in order. We currently only test bundle1 because bundle2 is substantially harder to test because it is more complicated (the server responds with a stream containing a bundle2 instead of a frame). Differential Revision: https://phab.mercurial-scm.org/D2471