CI: Split Flatpak beta and stable branches

We currently publish the same build from the same branch
to Flathub. However, soon we'll need to build the Flatpak
manifest in different branches, and publish them in different
repositories.

Prepare for that by splitting the publish step in two: one
for Flathub, and another for Flathub Beta. Do that using
a matrix strategy.

.github/workflows/flatpak.yml

@@ -67,29 +67,44 @@ jobs:
     container:
       image: bilelmoussaoui/flatpak-github-actions:kde-5.15-21.08
       options: --privileged
+    strategy:
+      matrix:
+        branch: [stable, beta]
     steps:
+      - name: Check if job should run
+        id: should_run
+        if: "${{ matrix.branch != 'stable' || (!contains(github.ref, '-beta') && !contains(github.ref, '-rc')) }}"
+        run: |
+          echo "Job should run"
+          echo "::set-output name=should_run::yes"
+
       - name: Checkout
         uses: actions/[email protected]
+        if: steps.should_run.outputs.should_run == 'yes'
         with:
           submodules: 'recursive'
 
       - name: Build Flatpak Manifest
         uses: bilelmoussaoui/flatpak-github-actions/flatpak-builder@master
+        if: steps.should_run.outputs.should_run == 'yes'
         with:
           bundle: obs-studio-${{ github.sha }}.flatpak
           manifest-path: CI/flatpak/com.obsproject.Studio.json
           cache-key: flatpak-builder-${{ github.sha }}
           mirror-screenshots-url: https://dl.flathub.org/repo/screenshots
+          branch: ${{ matrix.branch }}
 
       - name: Validate AppStream
         shell: bash
         working-directory: ${{ env.FLATPAK_BUILD_PATH }}
+        if: steps.should_run.outputs.should_run == 'yes'
         run: |
           appstream-util validate appdata/com.obsproject.Studio.appdata.xml
 
       - name: Verify icon and metadata in app-info
         shell: bash
         working-directory: ${{ env.FLATPAK_BUILD_PATH }}
+        if: steps.should_run.outputs.should_run == 'yes'
         run: |
           test -f app-info/icons/flatpak/128x128/com.obsproject.Studio.png || { echo "Missing 128x128 icon in app-info" ; exit 1; }
           test -f app-info/xmls/com.obsproject.Studio.xml.gz || { echo "Missing com.obsproject.Studio.xml.gz in app-info" ; exit 1; }
@@ -100,14 +115,15 @@ jobs:
 
       - name: Publish to Flathub Beta
         uses: bilelmoussaoui/flatpak-github-actions/flat-manager@v4
+        if: steps.should_run.outputs.should_run == 'yes' && matrix.branch == 'beta'
         with:
           flat-manager-url: https://hub.flathub.org/
           repository: beta
           token: ${{ secrets.FLATHUB_BETA_TOKEN }}
 
       - name: Publish to Flathub
         uses: bilelmoussaoui/flatpak-github-actions/flat-manager@v4
-        if: "!contains(github.ref, '-beta') && !contains(github.ref, '-rc')"
+        if: steps.should_run.outputs.should_run == 'yes' && matrix.branch == 'stable'
         with:
           flat-manager-url: https://hub.flathub.org/
           repository: stable