Merge pull request #79976 from bhipple/feature/fetchcargo-readme

rust: Replace migration README with GitHub issue

pkgs/build-support/rust/README.md

@@ -1,45 +0,0 @@
-# Updated fetchCargo behavior
-
-Changes to the `fetchcargo.nix` behavior that cause changes to the `cargoSha256`
-are somewhat disruptive, so historically we've added conditionals to provide
-backwards compatibility. We've now accumulated enough of these that it makes
-sense to do a clean sweep updating hashes, and delete the conditionals in the
-fetcher to simplify maintenance and implementation complexity. These
-conditionals are:
-
-1. When cargo vendors dependencies, it generates a config. Previously, we were
-   hard-coding our own config, but this fails if there are git dependencies. We
-   have conditional logic to sometimes copy the vendored cargo config in, and
-   sometimes not.
-
-2. When a user updates the src package, they may forget to update the
-   `cargoSha256`. We have an opt-in conditional flag to add the `Cargo.lock`
-   into the vendor dir for inspection and compare at build-time, but it defaults
-   to false.
-
-3. We were previously vendoring into a directory with a recursive hash, but
-   would like to vendor into a compressed tar.gz file instead, for the reasons
-   specified in the git commit message adding this feature.
-
-
-## Migration plan
-
-1. (DONE in this PR) Implement `fetchCargoTarball` as a separate, clean fetcher
-   implementation along-side `fetchcargo`. Rename `verifyCargoDeps` (default
-   false) to `legacyCargoFetcher` (default true), which switches the fetcher
-   implementation used. Replace `verifyCargoDeps = true;` with
-   `legacyCargoFetcher = false;` in Rust applications.
-
-2. Send a treewide Rust PR that sets `legacyCargoFetcher = true;` in all Rust
-   applications not using this (which is ~200 of them), with a note to
-   maintainers to delete if updating the package. Change the default in
-   `buildRustPackage` to false.
-
-3. Go through all Rust src packages deleting the `legacyCargoFetcher = false;`
-   line and re-computing the `cargoSha256`, merging as we go.
-
-4. Delete the `fetchcargo.nix` implementation entirely and also remove:
-  - All overrides in application-level packages
-  - The `fetchcargo-default-config.toml` and conditionals around using it when
-    no `$CARGO_CONFIG` exists
-  - This README.md file