in jps-wrapper/src/main/java/org/jetbrains/jps/model/serialization/JpsProjectLoader.java [103:111]
public static void loadProject(@NotNull JpsProject project,
@NotNull Map<String, String> pathVariables,
@NotNull JpsPathMapper pathMapper,
@NotNull Path projectPath,
boolean loadUnloadedModules,
@Nullable Path externalConfigurationDirectory) throws IOException {
loadProject(project, pathVariables, pathMapper, projectPath, null, externalConfigurationDirectory, DefaultExecutorHolder.threadPool,
loadUnloadedModules);
}