Add separate Webpacker integration test for Rails6

This proved too unreliable to mix with the other Rails versions (matrix workflows all fail if one fails).

If somebody wants to figure out why this doesn't work, be my guest. As Webpacker is no longer the Rails way (as of 7), I'm less concerned about this.

Author: jamesmartin

.github/workflows/rails_6_webpacker_integration_tests.yaml

@@ -0,0 +1,58 @@
+name: Rails 6 Webpacker Integration Tests (unreliable)
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        test-branch: [rails6-webpacker]
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Checkout test app
+      uses: actions/checkout@v2
+      with:
+        repository: jamesmartin/inline_svg_test_app
+        ref: ${{ matrix.test-branch }}
+        path: test_app
+    - name: Set up Ruby 2.7
+      uses: actions/setup-ruby@v1
+      with:
+        ruby-version: 2.7.x
+    - name: Build local gem
+      run: |
+        gem install bundler
+        bundle install --jobs 4 --retry 3
+        bundle exec rake build
+    - name: Use the local gem in the test App
+      id: uselocalgem
+      uses: jacobtomlinson/[email protected]
+      with:
+        find: "gem 'inline_svg'"
+        replace: "gem 'inline_svg', path: '${{github.workspace}}'"
+    - name: Check local gem in use
+      run: |
+        test "${{ steps.uselocalgem.outputs.modifiedFiles }}" != "0"
+        grep "inline_svg" $GITHUB_WORKSPACE/test_app/Gemfile
+    - name: Bundle
+      run: |
+        cd $GITHUB_WORKSPACE/test_app
+        bundle install --jobs 4 --retry 3
+    - name: Set up Node.js 16.x
+      uses: actions/setup-node@v2
+      with:
+        node-version: 16
+      if: matrix.test-branch == 'rails6-webpacker'
+    - name: Generate Webpacker config
+      run: |
+        cd $GITHUB_WORKSPACE/test_app
+        yarn install --check-files
+        bundle exec rake webpacker:compile
+      if: matrix.test-branch == 'rails6-webpacker'
+    - name: Test
+      run: |
+        cd $GITHUB_WORKSPACE/test_app
+        bundle exec rake test