Separate job action for creating Docker image

  - depends on build action
  - docker push is triggered only for branches 'master' and 'develop'

Author: anskarl

.github/workflows/main.yml

@@ -2,11 +2,14 @@ name: build
 
 on: [push, pull_request]
 
+env:
+  _JAVA_OPTIONS: "-Xms512m -Xmx4g"
+  REPOSITORY_OWNER: ${{ github.repository }}
+  LD_LIBRARY_PATH: "/usr/lib/lp_solve"
+
 jobs:
   build:
-
     runs-on: ubuntu-latest
-
     steps:
       - uses: actions/checkout@v2
         with:
@@ -18,16 +21,36 @@ jobs:
         uses: actions/setup-java@v1
         with:
           java-version: 1.8
+      - name: Cache SBT ivy cache
+        uses: actions/cache@v1
+        with:
+          path: ~/.ivy2/cache
+          key: ${{ runner.os }}-sbt-ivy-cache-${{ hashFiles('**/build.sbt') }}
+      - name: Cache SBT
+        uses: actions/cache@v1
+        with:
+          path: ~/.sbt
+          key: ${{ runner.os }}-sbt-${{ hashFiles('**/build.sbt') }}
       - name: Install lp_solve
         run: sudo apt update && sudo apt install -y bash lp-solve wget zip unzip && sudo rm -rf /var/lib/apt/lists/*
       - name: Install lp_solve java
         run: (cd /tmp && wget https://sourceforge.net/projects/lpsolve/files/lpsolve/5.5.2.5/lp_solve_5.5.2.5_java.zip && unzip lp_solve_5.5.2.5_java.zip && sudo cp lp_solve_5.5_java/lib/ux64/liblpsolve55j.so /usr/lib/lp_solve && sudo ldconfig && sudo rm -rf /tmp/lp_solve_5.5_java && rm /tmp/lp_solve_5.5.2.5_java.zip)
-      - name: Docker login
-        uses: azure/docker-login@v1
+      - name: Build for Scala 2.12
+        run: sbt ++2.12.10 clean compile
+      - name: Run Tests
+        run: sbt ++2.12.10 test
+
+  docker:
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
         with:
-          login-server: 'docker.pkg.github.com'
-          username: ${GITHUB_ACTOR}
-          password: ${{ secrets.GITHUB_TOKEN }}
+          fetch-depth: 1
+      - name: Set up JDK 1.8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.8
       - name: Cache SBT ivy cache
         uses: actions/cache@v1
         with:
@@ -38,16 +61,14 @@ jobs:
         with:
           path: ~/.sbt
           key: ${{ runner.os }}-sbt-${{ hashFiles('**/build.sbt') }}
-      - name: Build for Scala 2.12
-        run: sbt ++2.12.10 clean compile
-      - name: Run Tests
-        run: sbt ++2.12.10 test
+      - name: Docker login
+        uses: azure/docker-login@v1
+        with:
+          login-server: 'docker.pkg.github.com'
+          username: ${GITHUB_ACTOR}
+          password: ${{ secrets.GITHUB_TOKEN }}
       - name: Create Docker Image
         run: sbt ++2.12.10 docker
       - name: Push docker images
-        if: github.event_name != 'pull_request'
-        run: sbt ++2.12.10 dockerPush
-    env:
-      _JAVA_OPTIONS: "-Xms512m -Xmx4g"
-      REPOSITORY_OWNER: ${{ github.repository }}
-      LD_LIBRARY_PATH: "/usr/lib/lp_solve"
+        if: github.event_name == 'push' && (contains(github.ref, 'develop') || contains(github.ref, 'master'))
+        run: sbt ++2.12.10 dockerPush