code: def _normalize_merge_diff(diff):
          
          new_diff = []
          for line in diff.splitlines():
              # Filter blank lines and prepend +sign
              if line.strip():
                  new_diff.append("+" + line)
          if new_diff:
              new_diff.insert(
                  0, "! incremental-diff failed; falling back to echo of merge file"
              )
          else:
              new_diff.append("! No changes specified in merge file.")
          return "\n".join(new_diff)
docs: Make compare_config() for merge look similar to replace config diff.