Add step summary

run-scalafmt.sh

@@ -1,2 +1,29 @@
 #!/bin/sh
-scalafmt --non-interactive $args
+output=$(mktemp)
+warnings=$(mktemp)
+scalafmt --non-interactive $args > "$output" 2> "$warnings"
+result=$?
+cat "$output"
+cat "$warnings" >&2
+[ $result -eq 0 ] && exit
+
+report() {
+    file="$1"
+    summary="$2"
+
+    [ -s "$file" ] || return
+    echo "<details><summary>$summary</summary>"
+    echo
+    echo '```'
+    cat "$file"
+    echo '```'
+    echo '</details>'
+    echo
+}
+
+(
+    echo "# scalafmt failed ($result)"
+    report "$output" "Output"
+    report "$warnings" "Warnings"
+) >> "$GITHUB_STEP_SUMMARY"
+exit $result