DRY common code to build website into shared action

.github/actions/build_website/action.yaml

@@ -0,0 +1,13 @@
+name: Build the website
+description: Build the website
+
+runs:
+  using: "composite"
+  steps:
+    - name: Install the tutorial_web binary
+      shell: bash
+      run: /usr/bin/env python3 install.py linux
+
+    - name: Build
+      shell: bash
+      run: ./bin/tutorial_web build -i courses -s ./bin/static -o build -b /tutorial_web_content

.github/workflows/build.yml

@@ -1,15 +1,13 @@
-name: Builds the website (doesn't deploy - only used for checking syntax)
+name: Build the website (doesn't deploy - only used for checking syntax)
 
-on:
-  push
+on: [push, pull_request]
 
 jobs:
-  build-deploy:
+  build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
-    - name: Install the tutorial_web binary
-      run: /usr/bin/env python3 install.py linux
-    # Build the website
-    - name: Build
-      run: ./bin/tutorial_web build -i courses -s ./bin/static -o build -b /tutorial_web_content
+      - name: Checkout
+        uses: actions/checkout@master
+
+      - name: Build
+        uses: ./.github/actions/build_website

.github/workflows/github_pages_deploy.yml

@@ -9,14 +9,14 @@ jobs:
   build-deploy:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
-    - name: Install the tutorial_web binary
-      run: /usr/bin/env python3 install.py linux
-    # Build the website
-    - name: Build
-      run: ./bin/tutorial_web build -i courses -s ./bin/static -o build -b /tutorial_web_content
-    - name: Deploy
-      uses: JamesIves/github-pages-deploy-action@4.1.5
-      with:
-        branch: gh-pages
-        folder: build
+      - name: Checkout
+        uses: actions/checkout@master
+
+      - name: Build
+        uses: ./.github/actions/build_website
+
+      - name: Deploy
+        uses: JamesIves/github-pages-deploy-action@4.1.5
+        with:
+          branch: gh-pages
+          folder: build