## Summary
Split the old all-in-one `rust-ci.yml` into:
- a PR-time Cargo workflow in `rust-ci.yml`
- a full post-merge Cargo workflow in `rust-ci-full.yml`
This keeps the PR path focused on fast Cargo-native hygiene plus the
Bazel `build` / `test` / `clippy` coverage in `bazel.yml`, while moving
the heavyweight Cargo-native matrix to `main`.
## Why
`bazel.yml` is now the main Rust verification workflow for pull
requests. It already covers the Bazel build, test, and clippy signal we
care about pre-merge, and it also runs on pushes to `main` to re-verify
the merged tree and help keep the BuildBuddy caches warm.
What was still missing was a clean split for the Cargo-native checks
that Bazel does not replace yet. The old `rust-ci.yml` mixed together:
- fast hygiene checks such as `cargo fmt --check` and `cargo shear`
- `argument-comment-lint`
- the full Cargo clippy / nextest / release-build matrix
That made every PR pay for the full Cargo matrix even though most of
that coverage is better treated as post-merge verification. The goal of
this change is to leave PRs with the checks we still want before merge,
while moving the heavier Cargo-native matrix off the review path.
## What Changed
- Renamed the old heavyweight workflow to `rust-ci-full.yml` and limited
it to `push` on `main` plus `workflow_dispatch`.
- Added a new PR-only `rust-ci.yml` that runs:
- changed-path detection
- `cargo fmt --check`
- `cargo shear`
- `argument-comment-lint` on Linux, macOS, and Windows
- `tools/argument-comment-lint` package tests when the lint itself or
its workflow wiring changes
- Kept the PR workflow's gatherer as the single required Cargo-native
status so branch protection can stay simple.
- Added `.github/workflows/README.md` to document the intended split
between `bazel.yml`, `rust-ci.yml`, and `rust-ci-full.yml`.
- Preserved the recent Windows `argument-comment-lint` behavior from
`e02fd6e1d3` in `rust-ci-full.yml`, and mirrored cross-platform lint
coverage into the PR workflow.
A few details are deliberate:
- The PR workflow still keeps the Linux lint lane on the
default-targets-only invocation for now, while macOS and Windows use the
broader released-linter path.
- This PR does not change `bazel.yml`; it changes the Cargo-native
workflow around the existing Bazel PR path.
## Testing
- Rebasing this change onto `main` after `e02fd6e1d3`
- `ruby -e 'require "yaml"; %w[.github/workflows/rust-ci.yml
.github/workflows/rust-ci-full.yml .github/workflows/bazel.yml].each {
|f| YAML.load_file(f) }'`
