rhg: add rhg crate The goal of rhg is to speedup some of hg's commands when possible by bypassing python entirely for the time being. It is by no means a replacement for hg as it will not support extentions or configuration and implement only a subset of hg's commands and options. Only use rhg if you understand what the tradeoffs are. Differential Revision: https://phab.mercurial-scm.org/D8610

hg-core: add FindRoot operation to find repository root path Differential Revision: https://phab.mercurial-scm.org/D8609

hg-core: add Operation interface for high-level hg operations A distinction is made between operations and commands. An operation is a high-level function of mercurial whereas a command is what is exposed by the cli. A single command can use several operations to achieve its goal. Differential Revision: https://phab.mercurial-scm.org/D8608

rust: do a clippy pass This is the result of running `cargo clippy` on hg-core/hg-cpython and fixing the lints that do not require too much code churn (and would warrant a separate commit/complete refactor) and only come from our code (a lot of warnings in hg-cpython come from `rust-cpython`). Most of those were good lints, two of them was the linter not being smart enough (or compiler to get up to `clippy`'s level depending on how you see it). Maybe in the future we could have `clippy` be part of the CI. Differential Revision: https://phab.mercurial-scm.org/D8635

fuzz: add config knob for PYTHON_CONFIG_FLAGS I'll clean this up once we get oss-fuzz to use Python 3.8 instead of 2.7, but for now we need a way to evolve the flags passed to python-config in lockstep with the Python version. Yuck. Differential Revision: https://phab.mercurial-scm.org/D8637

pyutil: this has taken so long to fix, I'm using 3.8 now Differential Revision: https://phab.mercurial-scm.org/D8636

merge with stable

tests: remove unused creation of file and outdated text It was forgotten to remove this in fb0de0bcd297.