revlog: move datafile opening in a method Having file operation centralized into a single spot help to factor common logic out. It is also the first step to simplify file handling during batch operation (eg: revlog cloning). However, that part does not seems to be a hotspot yet.

parseindex: implement context manager method on the wrapper This is needed for incoming cleanups.

parseindex: also forward keyword argument in a debug wrapper Otherwise, it gets in the way of a coming refactoring.

dumprevlog: handle being passed a mode parameter This makes it closer to an actual file opener. Otherwise, it gets in the way of a coming refactoring.

changelog: add the missing 'closed' property on 'appender' object This mimic file object further.

changelog: implement context manager method for 'appender' object This object mimics a file and was missing the context manager API.

diff: improve ui.write performance when not coloring on Windows Differential Revision: https://phab.mercurial-scm.org/D2022

hgsh: enable clang-format Nothing looks awful, so we can just turn it on. Differential Revision: https://phab.mercurial-scm.org/D2059

chg: enable clang-format on all .c and .h files Nothing in here looks awful, so I think we may as well just do it. # skip-blame because it's just reformatting with no functionality change Differential Revision: https://phab.mercurial-scm.org/D2058

python3: whitelist an additional 11 tests I think these are mostly the result of Pulkit's recent work. Thanks! Differential Revision: https://phab.mercurial-scm.org/D2078