Update crate documentation of rustc_baked_icu_data crate

compiler/rustc_baked_icu_data/src/lib.rs

@@ -1,28 +1,27 @@
-//! Baked ICU data for eager translation support.
+//! This crate contains pre-baked ICU4X data, generated by `icu4x-datagen`. The tool
+//! fetches locale data from CLDR and transforms them into const code in statics that
+//! ICU4X can load, via databake. `lib.rs` in this crate is manually written, but all
+//! other code is generated.
 //!
+//! This crate can be regenerated when there's a new CLDR version, though that is unlikely
+//! to result in changes in most cases (currently this only covers list formatting data, which
+//! is rather stable). It may need to be regenerated when updating ICU4X versions, especially
+//! across major versions, in case it fails to compile after an update.
+//!
+//! It must be regenerated when adding new locales to Rust, or if Rust's usage of ICU4X
+//! grows to need more kinds of data.
+//!
+//! To regenerate the data, run this command:
+//!
+//! ```text
+//! icu4x-datagen -W --pretty --fingerprint --use-separate-crates \
+//! --format mod -l en es fr it ja pt ru tr zh zh-Hans zh-Hant \
+//! -k list/and@1 fallback/likelysubtags@1 fallback/parents@1 fallback/supplement/co@1 \
+//! --cldr-tag latest --icuexport-tag latest -o src/data
+//! ```
 #![allow(elided_lifetimes_in_paths)]
 
-/* generated with:
-```text
-icu4x-datagen -W --pretty --fingerprint --use-separate-crates --cldr-tag latest --icuexport-tag latest \
---format mod -l en es fr it ja pt ru tr zh zh-Hans zh-Hant -k list/and@1 fallback/likelysubtags@1 fallback/parents@1 fallback/supplement/co@1 \
--o src/data
-```
-*/
-
-// FIXME: Workaround https://github.com/unicode-org/icu4x/issues/2815
 mod data {
-    /*
-    use super::data::BakedDataProvider;
-    use icu_provider::{
-        AnyPayload, AnyProvider, AnyResponse, DataError, DataErrorKind, DataKey, DataRequest,
-        KeyedDataMarker,
-    };
-
-    use crate::data::fallback;
-    use crate::data::list;
-     */
-
     include!("data/mod.rs");
     include!("data/any.rs");
 }