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