Give the user the choice to parse SystemHooks

gitlab/gitlab.go

@@ -89,9 +89,6 @@ func (hook Webhook) Parse(r *http.Request, events ...Event) (interface{}, error)
 		return nil, ErrInvalidHTTPMethod
 	}
 
-	// Add SystemHookEvents to event slice to allow parsing
-	events = append(events, SystemHookEvents)
-
 	// If we have a Secret set, we should check the MAC
 	if len(hook.secret) > 0 {
 		signature := r.Header.Get("X-Gitlab-Token")

gitlab/gitlab_test.go

@@ -306,7 +306,7 @@ func TestSystemHooks(t *testing.T) {
 			var parseError error
 			var results interface{}
 			server := newServer(func(w http.ResponseWriter, r *http.Request) {
-				results, parseError = hook.Parse(r, tc.event)
+				results, parseError = hook.Parse(r, SystemHookEvents, tc.event)
 			})
 			defer server.Close()
 			req, err := http.NewRequest(http.MethodPost, server.URL+path, payload)