thirdparty: vendor cbor2 python library CBOR stands for Concise Binary Object Representation, which is a data format which is very compact and extensible. This patch moves the python library which can serilaize and deserialize python objects to/from cbor formats. The library is taken from https://github.com/agronholm/cbor2/ from commit 84181540f6eb650437e3f73cd104a65661fe8e67. Unrequired files from the cbor library - docs/, tests/, setup.py, setup.cfg, and tox.ini - have not been vendored. There is another python library for cbor at https://github.com/brianolson/cbor_py/ which is used in evolve extension and was imported in initial version of this series. That library though contains C code and is bit faster, but has known bugs around serializing nested structures, is unmaintained, raises an Exception object instead of a more dedicated Error type. So, it's better to use a bug free and actively maintained library. This library is not yet used and will be used in later commits. # no-check-commit because we are importing a third library module Differential Revision: https://phab.mercurial-scm.org/D2750

merge: deprecate accessing update results by index Now that we have named attributes, let's convert the code base to use them. We also add deprecation warnings so legacy consumers are aware of their transgressions. ``stats.unresolvedcount`` is much easier to read than ``stats[3]``, don't you think? Differential Revision: https://phab.mercurial-scm.org/D2694

procutil: introduce context-manager interface for protect/restorestdio The code looks slightly cleaner since it was pretty easy to pass arguments in wrong order.

procutil: move protectio/restoreio from commandserver Some variants of this will be useful for stdio-based servers such as sshserver.

commandserver: rewrite protectio/restoreio to not depend on ui Prepares for porting to utils.procutil, in which ui shouldn't be known. ui.flush() is replaced with ui.fout.flush() since ui.ferr wasn't involved.

util: deprecate procutil proxy functions (API) Several functions are re-exported by utils.procutil, which require explicit modname parameter. .. api:: Utility functions related to process/executable management have been moved to utils.procutil module.