[ci/rust] bumps workflow

- runs workflow when
  - toolchain configuration changes
  - rustfmt configuration changes

- limits workflow concurrency

- no longer use actions-rs actions, which are outdated/archived, use plain run
  instead of actions

- use actions-rust-lang/setup-rust-toolchain to use toolchain file

- no longer check stable/beta/nightly but the pinned version, dependabot will
  bump/test to the next toolchain version

- determine msrv

- cargo fmt --check and clippy are run against version from toolchain file

- cargo check build and test are run against both msrv and toolchain file

- bumps actions/checkout

Author: wookietreiber

.github/workflows/rust.yml

@@ -6,6 +6,8 @@ on:
   pull_request:
     paths:
       - '.github/workflows/rust.yml'
+      - '.rustfmt.toml'
+      - 'rust-toolchain.toml'
       - 'Cargo.toml'
       - 'Cargo.lock'
       - '**.rs'
@@ -15,60 +17,100 @@ on:
       - wip/next
     paths:
       - '.github/workflows/rust.yml'
+      - '.rustfmt.toml'
+      - 'rust-toolchain.toml'
       - 'Cargo.toml'
       - 'Cargo.lock'
       - '**.rs'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 env:
   CARGO_TERM_COLOR: always
   CARGO_TERM_VERBOSE: true
 
 jobs:
 
-  test:
-    name: ubuntu-${{ matrix.toolchain }}
+  check:
+    name: cargo fmt --check and clippy
     runs-on: ubuntu-latest
 
-    strategy:
-      matrix:
-        toolchain: [stable, beta, nightly]
-
     steps:
 
       - name: checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: set up rust toolchain
-        uses: actions-rs/toolchain@v1
+        uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          profile: minimal
-          toolchain: ${{ matrix.toolchain }}
           components: clippy, rustfmt
+          rustflags: ''
 
-      - name: cargo check
-        uses: actions-rs/cargo@v1
-        with:
-          command: check
+      - name: check formatting
+        run: cargo fmt --check
 
       - name: cargo clippy
-        uses: actions-rs/cargo@v1
+        run: cargo clippy
+
+  msrv:
+    name: msrv
+    runs-on: ubuntu-latest
+
+    outputs:
+      msrv: ${{ steps.msrv.outputs.msrv }}
+
+    steps:
+
+      - name: checkout
+        uses: actions/checkout@v6
+
+      - name: install cargo-msrv
+        uses: taiki-e/install-action@v2
         with:
-          command: clippy
+          tool: cargo-msrv
 
-      - name: check formatting
-        uses: actions-rs/cargo@v1
+      - name: show cargo-msrv version
+        run: cargo msrv --version
+
+      - name: get msrv
+        run: |
+          msrv=$(cargo msrv show --output-format minimal)
+          echo "msrv=$msrv" >> "$GITHUB_OUTPUT"
+        id: msrv
+
+      - name: show msrv
+        run: echo ${{ steps.msrv.outputs.msrv }}
+
+  test:
+    name: cargo check, build and test
+    runs-on: ubuntu-latest
+    needs: msrv
+
+    strategy:
+      matrix:
+        toolchain:
+          - null # this will use rust-toolchain.toml
+          - ${{ needs.msrv.outputs.msrv }}
+
+    steps:
+
+      - name: checkout
+        uses: actions/checkout@v6
+
+      - name: set up rust toolchain
+        uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          command: fmt
-          args: -- --check
+          toolchain: ${{ matrix.toolchain }}
+
+      - name: cargo check
+        run: cargo check
 
       - name: cargo build
-        uses: actions-rs/cargo@v1
-        with:
-          command: build
+        run: cargo build
 
       - name: cargo test
-        uses: actions-rs/cargo@v1
-        with:
-          command: test
+        run: cargo test
 
 ...