Set python version based on file change

.github/workflows/sherlock_test.yml

@@ -7,12 +7,26 @@ on:
     branches: [ master ]
 
 jobs:
+  getchange:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.changes.outputs.matrix }}
+    steps:
+      - id: changes
+        run: |
+          URL="https://api.github.com/repos/sherlock-project/sherlock/pulls/${{ github.event.pull_request.number }}/files"
+          FILES=$(curl -s -X GET -G $URL | jq -r '.[] | .filename')
+          if echo $FILES | grep -q ".json"; then
+            echo "::set-output name=matrix::{\"include\":[{\"python\":\"3.8\"}]}"
+          else
+            echo "::set-output name=matrix::{\"include\":[{\"python\":\"3.6\" },{\"python\":\"3.7\"},{\"python\":\"3.8\"}]}"
+          fi
   build:
-
+    needs: getchange
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8]
+        python-version: ${{fromJson(needs.getchange.outputs.matrix)}}
 
     steps:
     - uses: actions/checkout@v2