CI: Try using only MSRV in tests & lints

.github/workflows/ci.yml

@@ -2,16 +2,19 @@ name: CI
 on:
   pull_request:
   push:
-    branches:
-      - master
+    #branches:
+    #  - master
+
+env:
+  MSRV: "1.70"
 
 jobs:
   check-msrv:
     name: Check
     strategy:
       matrix:
         toolchain:
-          - "1.70"
+          - msrv
           - stable
     runs-on: ubuntu-latest
     steps:
@@ -27,7 +30,7 @@ jobs:
       - name: Install toolchain
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: ${{ matrix.toolchain}}
+          toolchain: ${{ matrix.toolchain == 'msrv' && env.MSRV || 'stable' }}
 
       - uses: Swatinem/rust-cache@v2
 
@@ -46,8 +49,10 @@ jobs:
       - name: Remove the rust-toolchain.toml
         run: rm rust-toolchain.toml
 
-      - name: Install stable toolchain
-        uses: dtolnay/rust-toolchain@stable
+      - name: Install MSRV toolchain
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: "${{ env.MSRV }}"
 
       - uses: Swatinem/rust-cache@v2
 
@@ -67,9 +72,10 @@ jobs:
       - name: Remove the rust-toolchain.toml
         run: rm rust-toolchain.toml
 
-      - name: Install stable toolchain
-        uses: dtolnay/rust-toolchain@stable
+      - name: Install MSRV toolchain
+        uses: dtolnay/rust-toolchain@master
         with:
+          toolchain: "${{ env.MSRV }}"
           components: rustfmt, clippy
 
       - uses: Swatinem/rust-cache@v2