use full metadata tag name for variable substitution

Author: zisoft

src/common/variables.c

@@ -953,17 +953,15 @@ static char *_get_base_value(dt_variables_params_t *params, char **variable)
     for(GList* iter = dt_metadata_get_list(); iter; iter = iter->next)
     {
       dt_metadata_t *metadata = (dt_metadata_t *)iter->data;
-      gchar *prefix = g_utf8_strup(dt_metadata_get_tag_subkey(metadata->tagname), -1);
       gboolean found = FALSE;
-      if(_has_prefix(variable, prefix))
+      if(_has_prefix(variable, metadata->tagname))
       {
         GList *res = dt_metadata_get(params->imgid, metadata->tagname, NULL);
         if(res != NULL)
           	result = g_strdup((char *)res->data);
         g_list_free_full(res, g_free);
         found = TRUE;
       }
-      g_free(prefix);
       if(found) break;
     }
     dt_pthread_mutex_unlock(&darktable.metadata_threadsafe);

src/gui/gtkentry.c

@@ -291,7 +291,7 @@ void dt_gtkentry_variables_add_metadata(dt_metadata_t *metadata)
 {
   GtkTreeIter iter;
 
-  gchar *varname = g_utf8_strup(dt_metadata_get_tag_subkey(metadata->tagname), -1);
+  gchar *varname = g_strdup(metadata->tagname);
   gchar *description = g_strdup_printf("$(%s) - %s", varname, _("from metadata"));
   gtk_list_store_append(_completion_model, &iter);
   gtk_list_store_set(_completion_model, &iter,