rename to pr.yml and run only on pull requests

Author: Soroosh Sarabadani

.github/workflows/ci.yml renamed to .github/workflows/pr.yml

@@ -1,8 +1,5 @@
-# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
-name: Java CI with Maven
+name: Verify Pull Request
 on:
-  push:
-    branches: [ master ]
   pull_request:
     branches: [ master ]
 jobs:
@@ -20,7 +17,7 @@ jobs:
           key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
           restore-keys: |
             ${{ runner.os }}-maven-
-      - name: Set up JDK
+      - name: Set up Java and Maven
         uses: actions/setup-java@v1
         with:
           java-version: ${{ matrix.java }}