Add MSRV minimal versions in CI

Author: Empty2k12

.github/workflows/rust.yml

@@ -68,6 +68,12 @@ jobs:
         os: [ubuntu-latest, windows-latest, macOS-latest]
     steps:
       - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@nightly
+        if: matrix.rust.name == 'MSRV'
+      - name: cargo -Z minimal-versions update
+        run: |
+          cargo -Z minimal-versions update
+        if: matrix.rust.name == 'MSRV'
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{matrix.rust.toolchain}}
@@ -78,7 +84,7 @@ jobs:
             ~/.cargo/git
             ~/.cargo/registry
             target
-          key: "${{runner.os}} Rust ${{steps.rust-toolchain.outputs.cachekey}}"
+          key: "${{matrix.rust.toolchain}} on ${{runner.os}} Rust ${{steps.rust-toolchain.outputs.cachekey}}"
       - run: cargo test --lib
       - run: cargo test --doc