Reorganize code, change method name, & fix comments.

Change xml file reading code when importing a course.

common/lib/xmodule/xmodule/modulestore/split_mongo/split_draft.py

@@ -494,11 +494,14 @@ class DraftVersioningModuleStore(SplitMongoModuleStore, ModuleStoreDraftAndPubli
                 block_id = self.DEFAULT_ROOT_LIBRARY_BLOCK_ID
             new_usage_key = course_key.make_usage_key(block_type, block_id)
 
+            # Only the course import process calls import_xblock(). If the branch setting is published_only,
+            # then the non-draft blocks are being imported.
             if self.get_branch_setting() == ModuleStoreEnum.Branch.published_only:
-                # override existing draft (PLAT-297, PLAT-299). NOTE: this has the effect of removing
-                # any local changes w/ the import.
+                # Override any existing drafts (PLAT-297, PLAT-299). This import/publish step removes
+                # any local changes during the course import.
                 draft_course = course_key.for_branch(ModuleStoreEnum.BranchName.draft)
                 with self.branch_setting(ModuleStoreEnum.Branch.draft_preferred, draft_course):
+                    # Importing the block and publishing the block links the draft & published blocks' version history.
                     draft_block = self.import_xblock(user_id, draft_course, block_type, block_id, fields, runtime)
                     return self.publish(draft_block.location.version_agnostic(), user_id, blacklist=EXCLUDE_ALL, **kwargs)
 

common/lib/xmodule/xmodule/modulestore/tests/test_xml_importer.py

@@ -9,7 +9,7 @@ from xmodule.x_module import XModuleMixin
 from opaque_keys.edx.locations import Location
 from xmodule.modulestore import ModuleStoreEnum
 from xmodule.modulestore.inheritance import InheritanceMixin
-from xmodule.modulestore.xml_importer import _import_module_and_update_references
+from xmodule.modulestore.xml_importer import _update_and_import_module
 from xmodule.modulestore.tests.mongo_connection import MONGO_PORT_NUM, MONGO_HOST
 from opaque_keys.edx.locations import SlashSeparatedCourseKey
 from xmodule.tests import DATA_DIR
@@ -144,7 +144,7 @@ class RemapNamespaceTest(ModuleStoreNoSettings):
 
         # Move to different runtime w/ different course id
         target_location_namespace = SlashSeparatedCourseKey("org", "course", "run")
-        new_version = _import_module_and_update_references(
+        new_version = _update_and_import_module(
             self.xblock,
             modulestore(),
             999,
@@ -181,7 +181,7 @@ class RemapNamespaceTest(ModuleStoreNoSettings):
 
         # Remap the namespace
         target_location_namespace = Location("org", "course", "run", "category", "stubxblock")
-        new_version = _import_module_and_update_references(
+        new_version = _update_and_import_module(
             self.xblock,
             modulestore(),
             999,
@@ -213,7 +213,7 @@ class RemapNamespaceTest(ModuleStoreNoSettings):
 
         # Remap the namespace
         target_location_namespace = Location("org", "course", "run", "category", "stubxblock")
-        new_version = _import_module_and_update_references(
+        new_version = _update_and_import_module(
             self.xblock,
             modulestore(),
             999,