Cache CI builds.

.github/workflows/build-and-test.yml

@@ -10,6 +10,12 @@ jobs:
  runs-on: ubuntu-latest
  steps:
  - uses: actions/checkout@v4
+ - uses: Swatinem/rust-cache@v2
+ with:
+ # this line means that only the main branch writes to the cache
+ # benefits: save about 7s per workflow by skipping the actual cache write
+ # downsides: PRs that update rust version or changes deps will be slower to iterate on due to changes not being cached.
+ save-if: ${{ github.ref == 'refs/heads/main' }}
  - uses: dtolnay/rust-toolchain@stable
  - run: cargo build --workspace --all-features
  - run: cargo test --workspace --all-features
@@ -29,6 +35,9 @@ jobs:
  runs-on: ubuntu-latest
  steps:
  - uses: actions/checkout@v4
+ - uses: Swatinem/rust-cache@v2
+ with:
+ save-if: ${{ github.ref == 'refs/heads/main' }}
  - uses: dtolnay/rust-toolchain@stable
  with:
  components: clippy