in jps-wrapper/src/main/java/org/jetbrains/jps/model/serialization/JpsProjectLoader.java [94:101]
public static void loadProject(JpsProject project,
Map<String, String> pathVariables,
@NotNull JpsPathMapper pathMapper,
Path projectPath,
boolean loadUnloadedModules) throws IOException {
Path externalConfigurationDirectory = JpsProjectConfigurationLoading.getExternalConfigurationDirectoryFromSystemProperty();
loadProject(project, pathVariables, pathMapper, projectPath, loadUnloadedModules, externalConfigurationDirectory);
}