Add the ability to override the base module marking used in the RPM disttags

MBS uses the base module's stream that was buildrequired by the module
in the RPM disttags for that module build. The stream name may not be
ideal for all situations, so now this is customizable by setting the
xmd['mbs']['disttag_marking'] in the base module's modulemd.

module_build_service/utils/general.py

@@ -240,13 +240,36 @@ def get_rpm_release(module_build):
                     .format(module_build.id))
         buildrequires = None
 
-    base_module_stream = ''
+    # Determine which base module is buildrequired and its marking in the disttag
+    base_module_marking = ''
+    # If the buildrequires are recorded in the xmd then we can try to find the base module that
+    # is buildrequired
     if buildrequires:
+        # Looping through all the base modules in conf.base_module_names instead of looping through
+        # all the buildrequires guarantees the order in conf.base_module_names is preserved for
+        # which base module is used as the marking
         for base_module in conf.base_module_names:
-            base_module_stream = buildrequires.get(base_module, {}).get('stream', '')
-            if base_module_stream:
-                base_module_stream += '+'
-                break
+            bm_in_xmd = buildrequires.get(base_module)
+
+            if not bm_in_xmd:
+                continue
+
+            with models.make_session(conf) as session:
+                base_module_obj = models.ModuleBuild.get_build_from_nsvc(
+                    session, base_module, bm_in_xmd['stream'], bm_in_xmd['version'],
+                    bm_in_xmd['context'])
+            if not base_module_obj:
+                continue
+
+            # Default to using the base module's stream, but if the base module has disttag_marking
+            # set in the xmd, use that instead
+            try:
+                marking = base_module_obj.mmd().get_xmd()['mbs']['disttag_marking']
+            # We must check for a KeyError because a Variant object doesn't support the `get` method
+            except KeyError:
+                marking = base_module_obj.stream
+            base_module_marking = marking + '+'
+            break
         else:
             log.warning('Module build {0} does not buildrequire a base module ({1})'
                         .format(module_build.id, ' or '.join(conf.base_module_names)))
@@ -254,9 +277,9 @@ def get_rpm_release(module_build):
     # use alternate prefix for scratch module build components so they can be identified
     prefix = ('scrmod+' if module_build.scratch else conf.default_dist_tag_prefix)
 
-    return '{prefix}{base_module_stream}{index}+{dist_hash}'.format(
+    return '{prefix}{base_module_marking}{index}+{dist_hash}'.format(
         prefix=prefix,
-        base_module_stream=base_module_stream,
+        base_module_marking=base_module_marking,
         index=index,
         dist_hash=dist_hash,
     )

tests/test_utils/test_utils.py

@@ -336,6 +336,23 @@ class TestUtils:
         release = module_build_service.utils.get_rpm_release(build_one)
         assert release == 'module+f28+2+814cfa39'
 
+    def test_get_rpm_release_platform_stream_override(self):
+        scheduler_init_data(1)
+
+        # Set the disttag_marking override on the platform
+        platform = models.ModuleBuild.query.filter_by(name='platform', stream='f28').first()
+        platform_mmd = platform.mmd()
+        platform_xmd = glib.from_variant_dict(platform_mmd.get_xmd())
+        platform_xmd['mbs']['disttag_marking'] = 'fedora28'
+        platform_mmd.set_xmd(glib.dict_values(platform_xmd))
+        platform.modulemd = to_text_type(platform_mmd.dumps())
+        db.session.add(platform)
+        db.session.commit()
+
+        build_one = models.ModuleBuild.query.get(2)
+        release = module_build_service.utils.get_rpm_release(build_one)
+        assert release == 'module+fedora28+2+814cfa39'
+
     def test_get_rpm_release_mse_scratch(self):
         init_data(contexts=True, scratch=True)
         build_one = models.ModuleBuild.query.get(2)