Handle more cases

This should now handle:

- adding a sub-directory
- removing a sub-directory

tubesync/sync/signals.py

@@ -1,4 +1,5 @@
 from pathlib import Path
+from tempfile import TemporaryDirectory
 from django.conf import settings
 from django.db.models.signals import pre_save, post_save, pre_delete, post_delete
 from django.dispatch import receiver
@@ -29,15 +30,35 @@ def source_pre_save(sender, instance, **kwargs):
         return
     existing_dirpath = existing_source.directory_path.resolve(strict=True)
     new_dirpath = instance.directory_path.resolve(strict=False)
-    rename_source_directory = (
-        existing_dirpath != new_dirpath and
-        not new_dirpath.exists()
-    )
-    if rename_source_directory:
-        tmp_dirpath = existing_dirpath.parent / ('.tmp.' + existing_dirpath.name)
-        existing_dirpath.rename(tmp_dirpath)
+    if existing_dirpath != new_dirpath:
+        path_name = lambda p: p.name
+        relative_dir = existing_source.directory
+        rd_parents = Path(relative_dir).parents
+        rd_parents_set = set(map(path_name, rd_parents))
+        ad_parents = existing_dirpath.parents
+        ad_parents_set = set(map(path_name, ad_parents))
+        # the names in the relative path are also in the absolute path
+        parents_count = len(ad_parents_set.intersection(rd_parents_set))
+        work_directory = existing_dirpath
+        while parents_count > 0:
+            work_directory = work_directory.parent
+            parents_count -= 1
+        with TemporaryDirectory(suffix='.'+new_dirpath.name, prefix='.tmp.', dir=work_directory) as tmp_dir:
+            tmp_dirpath = Path(tmp_dir)
+            existed = None
+            if new_dirpath.exists():
+                existed = tmp_dirpath / 'existed'
+                new_dirpath.rename(existed)
+            previous = tmp_dirpath / 'previous'
+            existing_dirpath.rename(previous)
             mkdir_p(new_dirpath.parent)
-        tmp_dirpath.rename(new_dirpath)
+            previous.rename(new_dirpath)
+            if existed and existed.is_dir():
+                existed.rename(new_dirpath / '.existed')
+                # TODO: merge the contents of the directories
+                pass
+            elif existed:
+                existed.rename(new_dirpath / '.existed')
     recreate_index_source_task = (
         existing_source.name != instance.name or
         existing_source.index_schedule != instance.index_schedule