Unittests: blendfile versioning: Add Link and Append basic tests.

These are really basic testing as well, merely linking or appending the
first collection or object in all processed blendfiles. But it should
help catching 'rare' issues in linking/appending from older blendfiles.

tests/python/bl_blendfile_versioning.py

@@ -79,6 +79,24 @@ class TestBlendFileOpenAllTestFiles(TestHelper):
             bpy.ops.wm.read_homefile(use_empty=True, use_factory_startup=True)
             bpy.ops.wm.open_mainfile(filepath=bfp, load_ui=False)
 
+    def link_append(self, do_link):
+        for bfp in self.blendfile_paths:
+            if os.path.basename(bfp) in self.excluded_paths:
+                continue
+            bpy.ops.wm.read_homefile(use_empty=True, use_factory_startup=True)
+            with bpy.data.libraries.load(bfp, link=do_link) as (lib_in, lib_out):
+                if len(lib_in.collections):
+                    lib_out.collections.append(lib_in.collections[0])
+                elif len(lib_in.objects):
+                    lib_out.objects.append(lib_in.objects[0])
+
+
+    def test_link(self):
+        self.link_append(do_link=True)
+
+    def test_append(self):
+        self.link_append(do_link=False)
+
 
 TESTS = (
     TestBlendFileOpenAllTestFiles,