local cache (#152)

* use a local cache

Author: CohenCyril

.github/workflows/nix.yml

@@ -11,33 +11,70 @@ on:
     branches: [ master ]
 
 jobs:
-  nix:
+  hb:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
-      with:
-        fetch-depth: 0
-    - uses: cachix/install-nix-action@v12
-    - uses: cachix/cachix-action@v8
+    - name: Cachix install
+      uses: cachix/install-nix-action@v12
+    - name: Cachix setup
+      uses: cachix/cachix-action@v8
       with:
         name: math-comp
         extraPullNames: coq
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-    - run: nix-build
+    - name: Cache Nix Store
+      uses: actions/[email protected]
+      id: cache-nix
+      with:
+        path: nix-store.nar
+        key: nix-${{ runner.os }}-${{ github.sha }}
+        restore-keys: |
+          nix-${{ runner.os }}-
+    - name: Import Nix Store
+      if: steps.cache-nix.outputs.cache-hit
+      run: nix-store --import < nix-store.nar
+    - name: Git checkout
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+    - name: Build
+      run: nix-build
+    - name: Compute Closure
+      run: nix path-info --all | tee closure.txt
+    - name: Export Nix Store
+      run: xargs --arg-file=closure.txt nix-store --export > nix-store.nar
 
-  nixci:
+  mathcomp:
     runs-on: ubuntu-latest
-    needs: nix
-
+    needs: hb
     steps:
-    - uses: actions/checkout@v2
-      with:
-        fetch-depth: 0
-    - uses: cachix/install-nix-action@v12
-    - uses: cachix/cachix-action@v8
+    - name: Cachix install
+      uses: cachix/install-nix-action@v12
+    - name: Cachix setup
+      uses: cachix/cachix-action@v8
       with:
         name: math-comp
         extraPullNames: coq
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-    - run: nix-build --arg ci true
+    - name: Cache Nix Store
+      uses: actions/[email protected]
+      id: cache-nix
+      with:
+        path: nix-store.nar
+        key: nix-${{ runner.os }}-${{ github.sha }}
+        restore-keys: |
+          nix-${{ runner.os }}-
+    - name: Import Nix Store
+      if: steps.cache-nix.outputs.cache-hit
+      run: nix-store --import < nix-store.nar
+    - name: Git checkout
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+    - name: Build
+      run: nix-build --arg ci true
+    - name: Compute Closure
+      run: nix path-info --all | tee closure.txt
+    - name: Export Nix Store
+      run: xargs --arg-file=closure.txt nix-store --export > nix-store.nar