builddep: Warning when using macros with source rpms (RhBug:2077820)

= changelog =
type: bugfix
resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2077820

doc/builddep.rst

@@ -31,7 +31,7 @@ All general DNF options are accepted, see `Options` in :manpage:`dnf(8)` for det
     Show this help.
 
 ``-D <macro expr>, --define <macro expr>``
-    Define the RPM macro named `macro` to the value `expr` when parsing spec files.
+    Define the RPM macro named `macro` to the value `expr` when parsing spec files. Does not apply for source rpm files.
 
 ``--spec``
     Treat arguments as .spec files.

plugins/builddep.py

@@ -204,6 +204,10 @@ def _src_deps(self, src_fn):
             err = _("Not all dependencies satisfied")
             raise dnf.exceptions.Error(err)
 
+        if self.opts.define:
+            logger.warning(_("Warning: -D or --define arguments have no meaning "
+                             "for source rpm packages."))
+
     def _spec_deps(self, spec_fn):
         try:
             spec = rpm.spec(spec_fn)