Finish move to GitHub Actions with build trigger

Closes: #5
PR: #13

Author: aepfli

.github/workflows/actions.yml

@@ -3,13 +3,17 @@ name: JUnit Pioneer Site
 on:
   push:
     branches: [ grandmaster, site-source ]
+  repository_dispatch:
+    types: [triggerSiteBuild]
 
 jobs:
   publish:
     runs-on: ubuntu-latest
     steps:
       - name: Check out repo
         uses: actions/checkout@v2
+        with:
+          ref: "grandmaster"
       - name: Set up Ruby
         uses: actions/setup-ruby@v1
         with:
@@ -23,9 +27,7 @@ jobs:
           ruby -v
           bundler -v
           java -version
-      - name: "Gradle: setup"
-        run: ./gradlew setup --no-daemon --stacktrace
-      - name: "Gradle: build site"
-        run: ./gradlew buildSite --no-daemon --stacktrace
-      - name: "Gradle: publish site"
-        run: ./gradlew pushSite --no-daemon --stacktrace
+      - name: Gradle setup, build and push
+        uses: eskatos/gradle-command-action@v1
+        with:
+          arguments: setup buildSite pushSite --no-daemon --stacktrace

README.md

@@ -49,6 +49,19 @@ With the correct credentials, `gradle pushSite` pushes the changes in `site` to
 For local experimentation with the site layout, it makes sense to first run `gradle buildSite` and then manually launch Jekyll in `site-source` with `bundle exec jekyll serve`.
 Note the `serve`, which launches a server on localhost (Jekyll messages list the port) and also watches the `site-source` directory for further changes.
 
+### Build Trigger
+
+Projects like [JUnit Pioneer (the expansion pack)](https://github.com/junit-pioneer/junit-pioneer) can trigger a site build with GitHub Actions with this step:
+
+```yaml
+- name: Trigger Website Build
+  uses: peter-evans/repository-dispatch@v1
+  with:
+    token: ${{ secrets.GH_WRITE_TOKEN }}
+    repository: junit-pioneer/junit-pioneer.github.io
+    event-type: triggerSiteBuild
+```
+
 
 ## Background