match: drop support for empty pattern list in patternmatcher Since the caller now deals with empty pattern lists, we can drop that support in the patternmatcher. It now gets the more logical behavior of matching nothing when no patterns are given (although there is no in-core caller that will pass no patterns).

match: optimize visitdir() for when no explicit files are listed In patternmatcher, we used to say that all directories should be visited if no explicit files were listed, because the case of empty _files usually implied that no patterns were given (which in turns meant that everything should match). However, this made e.g. "hg files -r . rootfilesin:." slower than necessary, because that also ended up with an empty list in _files. Now that patternmatcher does not handle includes, the only remaining case where its _files/_fileset fields will be empty is when it's matching everything. We can therefore treat the always-case specially and stop treating the empty _files case specially. This makes the case mentioned above faster on treemanifest repos.

match: handle everything-matching using new alwaysmatcher Having a special matcher that always matches seems to make more sense than making one of the other matchers handle the case. For now, we just use this new matcher when no patterns were provided.

match: add __repr__ for subdirmatcher Should at least be useful for debugging. Would matter for correctness too if fsmonitor or Facebook's sparse extension worked with subrepos (which I don't know if they do).

tests: make test-manifest.py portable to Python 3 Lots of b prefixes here, and https://bugs.python.org/issue29714 means that this test is still very broken on Python 3.6 and 3.6.1, but 3.6.2 should things (based on testing using tip of the 3.6 branch from git). #cleanup-only

cleanup: rename all iteritems methods to items and add iteritems alias Due to a quirk of our module importer setup on Python 3, all calls and definitions of methods named iteritems() get rewritten at import time. Unfortunately, this means there's not a good portable way to access these methods from non-module-loader'ed code like our unit tests. This change fixes that, which also unblocks test-manifest.py from passing under Python 3. We don't presently define any itervalues methods, or we'd need to give those similar treatment.

help: work around textwrap.dedent() only working on strings

server: write out pid using bytes IO instead of str IO

help: convert dict to strkwargs

util: use sysstr.join instead of bytes.join in textwrap wrapper