Update rust-toolchain to new toml syntax

This allows us to completely skip the "Install Rust" step in CI
because the rust-toolchain file completely describes what we need.
The first invocation of cargo will simply install all the required
components.

Additionally, we make all caches dependant on the version of Rust
that we require.

.github/workflows/ci.yml

@@ -15,19 +15,12 @@ jobs:
       - name: Checkout sources
         uses: actions/checkout@v2
 
-      - name: Install Rust
-        uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          override: true
-          components: rustfmt, clippy
-
       - name: Cache ~/.cargo/bin directory
         id: cargo-bin-cache
         uses: actions/cache@v2.1.4
         with:
           path: ~/.cargo/bin
-          key: ubuntu-rust-${{ env.RUST_TOOLCHAIN }}-cargo-bin-directory-v1
+          key: ubuntu-rust-${{ hashFiles('rust-toolchain') }}-cargo-bin-directory-v1
 
       - name: Install tomlfmt
         if: steps.cargo-bin-cache.outputs.cache-hit != 'true'
@@ -63,19 +56,13 @@ jobs:
       - name: Checkout sources
         uses: actions/checkout@v2
 
-      - name: Install Rust toolchain
-        uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          override: true
-
       - name: Cache target and registry directory
         uses: actions/cache@v2.1.4
         with:
           path: |
             target
             ~/.cargo/registry
-          key: rust-${{ matrix.target }}-build-${{ hashFiles('Cargo.lock') }}-v1
+          key: rust-${{ matrix.target }}-build-${{ hashFiles('Cargo.lock') }}-${{ hashFiles('rust-toolchain') }}-v1
 
       - name: Build binary
         run: |
@@ -110,19 +97,13 @@ jobs:
       - name: Checkout sources
         uses: actions/checkout@v2
 
-      - name: Install Rust toolchain
-        uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          override: true
-
       - name: Cache target and registry directory
         uses: actions/cache@v2.1.4
         with:
           path: |
             target
             ~/.cargo/registry
-          key: rust-${{ matrix.target }}-test-${{ hashFiles('Cargo.lock') }}-v1
+          key: rust-${{ matrix.target }}-test-${{ hashFiles('Cargo.lock') }}-${{ hashFiles('rust-toolchain') }}-v1
 
       - name: Build tests
         run: cargo build --tests --workspace --all-features
@@ -152,19 +133,13 @@ jobs:
       - name: Checkout sources
         uses: actions/checkout@v2
 
-      - name: Install Rust toolchain
-        uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          override: true
-
       - name: Cache target and registry directory
         uses: actions/cache@v2.1.4
         with:
           path: |
             target
             ~/.cargo/registry
-          key: rust-${{ matrix.target }}-test-${{ hashFiles('Cargo.lock') }}-v1
+          key: rust-${{ matrix.target }}-test-${{ hashFiles('Cargo.lock') }}-${{ hashFiles('rust-toolchain') }}-v1
 
       - name: Run test ${{ matrix.test_name }}
         run: cargo test --package swap --all-features --test ${{ matrix.test_name }} ""

rust-toolchain

@@ -1 +1,3 @@
-nightly-2021-01-31
+[toolchain]
+channel = "nightly-2021-01-31"
+components = ["rustfmt", "clippy"]