fixup! chore: add CI to publish Flatpak to Mixxx repo

Author: acolombier

.github/workflows/flatpak.yml

@@ -59,13 +59,12 @@ jobs:
             echo "branch=beta" >> $GITHUB_OUTPUT
             echo "expiry=30 days" >> $GITHUB_OUTPUT
           elif [ "$REF" = "refs/heads/main" ]; then
-            echo "commit_summary=Alpha build for 2.7" >> $GITHUB_OUTPUT
-            echo "branch=alpha" >> $GITHUB_OUTPUT
+            echo "commit_summary=Nightly build for 2.7" >> $GITHUB_OUTPUT
+            echo "branch=nightly" >> $GITHUB_OUTPUT
             echo "expiry=14 days" >> $GITHUB_OUTPUT
           else
-            echo "commit_summary=Snapshot build for ${GITHUB_SHA}" >> $GITHUB_OUTPUT
-            echo "branch=snapshot" >> $GITHUB_OUTPUT
-            echo "expiry=7 days" >> $GITHUB_OUTPUT
+            echo "::error:: The git reference is unsupported for publication to the Flatpak repo."
+            exit 1
           fi
 
       - name: "Download bundles"