ubuntu.yml in metanorma-rsd-1.4.7

- old
+ new

@@ -4,18 +4,26 @@
 
 on:
   push:
     branches: [ master ]
   pull_request:
+    paths-ignore:
+      - .github/workflows/macos.yml
+      - .github/workflows/windows.yml
 
 jobs:
   test-linux:
     name: Test on Ruby ${{ matrix.ruby }} Ubuntu
     runs-on: ubuntu-latest
+    continue-on-error: ${{ matrix.experimental }}
     strategy:
       fail-fast: false
       matrix:
         ruby: [ '2.6', '2.5', '2.4' ]
+        experimental: [false]
+        include:
+          - ruby: '2.7'
+            experimental: true
     steps:
       - uses: actions/checkout@master
       - name: Use Ruby
         uses: actions/setup-ruby@v1
         with: