Fix bugs with the custom git trigger and make error reporting better

endpoints/trigger.py

@@ -991,7 +991,7 @@ class CustomBuildTrigger(BuildTriggerHandler):
         'required': ['url', 'message', 'date'],
       },
     },
-    'required': ['commits', 'ref', 'default_branch'],
+    'required': ['commit', 'ref', 'default_branch'],
   }
 
   @classmethod
@@ -1005,15 +1005,15 @@ class CustomBuildTrigger(BuildTriggerHandler):
     try:
       metadata = json.loads(payload)
       validate(metadata, self.payload_schema)
-    except:
-      raise InvalidPayloadException()
+    except Exception as e:
+      raise InvalidPayloadException(e.message)
     return metadata
 
   def handle_trigger_request(self, request):
     # Skip if there is no payload.
-    payload = request.get_json()
+    payload = request.data
     if not payload:
-      raise SkipRequestException()
+      raise InvalidPayloadException()
 
     logger.debug('Payload %s', payload)
 
@@ -1028,9 +1028,10 @@ class CustomBuildTrigger(BuildTriggerHandler):
 
     prepared = PreparedBuild(self.trigger)
     prepared.tags_from_ref(metadata['ref'])
-    prepared.name_from_sha(metadata['commit_sha'])
+    prepared.name_from_sha(metadata['commit'])
     prepared.subdirectory = config['subdir']
     prepared.metadata = metadata
+    prepared.is_manual = False
 
     return prepared