rust: Move config value parsing functions to a new module Differential Revision: https://phab.mercurial-scm.org/D10021

rhg: Add support for the blackbox extension Only `command` and `commandfinish` events are logged. The `dirty`, `logsource`, `track` and `ignore` configuration items are not supported yet. To indicate commands executed without Python, a `(rust) ` prefix is added in corresponding log messages. Differential Revision: https://phab.mercurial-scm.org/D10012

blackbox: Remove misleading quotes in config example This example previously looked like quotes were part of configuration file syntax, and the parsed `date-format` value was the part inside of them. This is not the case: config syntax only parses quotes in list values. Instead using that config would result in literal quotes being written to `.hg/blackbox.log` as part of the date format. This changes the example to what was probably intended. Differential Revision: https://phab.mercurial-scm.org/D10011

rust: Add a log file rotation utility This is ported to Rust from `mercurial/loggingutil.py`. The "builder" pattern is used to make it visible at call sites what the two numeric parameters mean. In Python they might simply by keyword arguments. Differential Revision: https://phab.mercurial-scm.org/D10010

rust: Add a `ConfigValueParseError` variant to common errors Configuration files are parsed into sections of key/value pairs when they are read, but at that point values are still arbitrary bytes. Only when a value is accessed by various parts of the code do we know its expected type and syntax, so values are parsed at that point. Let’s make a new error type for this latter kind of parsing error, and add a variant to the common `HgError` so that most code can propagate it without much boilerplate. Differential Revision: https://phab.mercurial-scm.org/D10009

rust: Add config parsing support for more value types * Rust `str` (ASCII or UTF-8) * Integer * Byte quantities Differential Revision: https://phab.mercurial-scm.org/D10008

rust: Introduce a get_bytes_from_os_str utility function It does the same as get_bytes_from_path but takes an `OsStr` instead of a `Path`. The implementation is the same so using either ends up correct but the function name suggests it’s not. Differential Revision: https://phab.mercurial-scm.org/D10007

rust: Make `DirstateParents`’s fields typed `Node`s Instead of plain byte arrays. Differential Revision: https://phab.mercurial-scm.org/D10006

rust: Rewrite dirstate parsing usin the `bytes-cast` crate Differential Revision: https://phab.mercurial-scm.org/D10005

rhg: Move `Repo` object creation into `main()` … rather than in each sub-command that needs a local repository. This will allow accessing e.g. `.hg/blackbox.log` before dispatching to sub-commands. Differential Revision: https://phab.mercurial-scm.org/D10004

rhg: Group values passed to every sub-command into a struct The set of which values this is is evidently not stable yet, so this will make changes easier. Also it is growing, and the function signatures are getting out hand. Differential Revision: https://phab.mercurial-scm.org/D10003

rhg: Remove error message on unsupported CLI arguments Like in other "unsupported" cases that return a specific exit code Differential Revision: https://phab.mercurial-scm.org/D10002