Meta: do not create release when there are no public changes (#401)

.github/scripts/changelog.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+release_has_public_changes=false
+
 url=$(git remote get-url origin | sed -r 's/(.*)\.git/\1/')
 
 previous_tag=$(git describe --tags --abbrev=0 HEAD~)
@@ -23,5 +25,12 @@ do
             # Escape markdown formatting symbols _ * `
             echo "  $line" | sed 's/_/\\_/g' | sed 's/`/\\`/g' | sed 's/\*/\\\*/g'
         done
+        release_has_public_changes=true
     fi
 done
+
+if ! $release_has_public_changes
+then
+    echo "No public changes since $previous_tag." >&2
+    exit 1
+fi

.github/workflows/release.yaml

@@ -20,10 +20,13 @@ jobs:
         run: tar -czf forgit-${{github.ref_name}}.tar.gz --exclude LICENSE --exclude README.md *
 
       - name: Generate Changelog
+        id: changelog
         run: .github/scripts/changelog.sh > CHANGELOG.md
+        continue-on-error: true
 
       - name: Release
         uses: softprops/action-gh-release@v2
+        if: steps.changelog.outcome == 'success'
         with:
           body_path: CHANGELOG.md
           files: forgit-${{github.ref_name}}.tar.gz