When a PR restores the cache, it will find the most recent cache from
the `main` branch. This cache should be mostly up to date.
We are constantly at the 10 GB limit for our CI caches, so removing the
extra caches from the many PR branches should ensure that we always have
space for the `main` branch caches.
The i18n-helpers are now available as a stand-alone crate:
https://crates.io/crates/mdbook-i18n-helpers.
Because we cache the Rust binaries in our GitHub workflows, I bumped
the cache prefix to ensure we use a clean cache. Otherwise, Cargo
won’t install the new binaries in mdbook-i18n-helpers because it sees
the old ones from this repository.
* Move Cargo.toml for exercises to exercises directory.
* Create a workspace with both exercises and i18n-helpers.
* Build in CI as well as testing.
* Binaries must have a main function.
* No need for workspaces configuration for caching anymore.
* Extract common build steps to composite actions
This allows us to repeat ourselves less across the different jobs.
I also tested using a “reusable workflow” to factor out the common
steps. However, this starts a separate job without a shared
filesystem, which in turn requires us to upload/download artifacts
when we want to use them in several jobs. The artifacts are downloaded
one-by-one and this adds delays and extra steps to all jobs.
* Move Rust cache setup to its own build step
This made it easy to consistently setup the caching of our nested
projects via the “workspacs” config key.
