CI: cache-deps: mk src caching depend on pinned Hackage timestamp

Author: Anton-Latukha

.github/workflows/cache-deps.yml

@@ -65,9 +65,11 @@ jobs:
           echo "package floskell" >> cabal.project
           echo "  ghc-options: -O0" >> cabal.project
 
-      # NOTE: Freeze is for the caching
-      - name: "Configuration freeze"
-        run: cabal v2-freeze --enable-tests --enable-benchmarks
+      - if: ( runner.os == 'Linux' ) || ( runner.os == 'macOS' )
+        name: (Linux,macOS) Platform config
+        run: |
+          TIMESTAMP="$(grep index-state cabal.project)"
+          echo "HACKAGE_TIMESTAMP=$TIMESTAMP" >> $GITHUB_ENV
 
       - name: Hackage sources cache
         uses: actions/cache@v2
@@ -76,9 +78,13 @@ jobs:
         with:
           path: ${{ env.CABAL_PKGS_DIR }}
           #  2021-12-01: NOTE: Cabal Hackage source tree storage does not depend on OS or GHC.
-          key:          ${{ env.cache-name }}-${{ hashFiles('cabal.project.freeze') }}
+          key:          ${{ env.cache-name }}-${{ env.HACKAGE_TIMESTAMP }}
           restore-keys: ${{ env.cache-name }}-
 
+      # NOTE: Freeze is for the caching
+      - name: "Configuration freeze"
+        run: cabal v2-freeze --enable-tests --enable-benchmarks
+
       - name: Compiled deps cache
         uses: actions/cache@v2
         env: