fix: improved error message in case of target rule misspecification

snakemake/dag.py

@@ -1653,7 +1653,10 @@ def rule2job(self, targetrule):
         """Generate a new job from a given rule."""
         if targetrule.has_wildcards():
             raise WorkflowError(
-                "Target rules may not contain wildcards. Please specify concrete files or a rule without wildcards."
+                "Target rules may not contain wildcards. "
+                "Please specify concrete files or a rule without wildcards at the command line, "
+                "or have a rule without wildcards at the very top of your workflow (e.g. the typical "
+                '"rule all" which just collects all results you want to generate in the end).'
             )
         return self.new_job(targetrule)