repoview: fix the filter created by `extrafilter` The `name` variable was updated in each interaction of the loop, making all new filters inheriting from the same base (the last one iterated), leading to terrible terrible misbehavior.

repoview: show `extrafilter` misbehave when other filtering is in play See new changeset for fix and details.

rust-config: add docstring to inner `get_parse` method The signature is quite heavy, a docstring to explain the idea doesn't hurt.

rust-config: add devel warning when using undeclared config items This mirrors the Python implementation now that we're done catching up.

rhg: use default configitem in `cat` Now that we've declared the items, we can get rid of the manual fallback.

rhg: add config defaults to configitems.toml This will allow us to use the same default config mechanic as the rest of the code.

rust-blackbox: use `is_extension_enabled` config helper It's there, may as well use it to make the code clearer and less bug-prone.

configitems: move blackbox's config items to the new configitems.toml In order for the Rust code to gain access to default values of in-core extensions that have a Rust implementation, we need to centralize them alongside the core items declarations. This is the first and so far only one of the extensions that have gained Rust support, I don't think it's worth the churn to move the rest of the extension's configitems yet.

rust-config: add config getters that don't fall back to defaults This is useful in cases where we access config items that are more... lenient with their types than a fresh new system would allow. For now there is only a single use of this, but we might get more later.

rust-config: add support for default config items Now that configitems.toml exists, we can read from it the default values for all core config items. We will add the devel-warning for use of undeclared config items in a later patch when we're done adding the missing entries for `rhg`.