Cleanup comments

Author: MarcelGeo

server/mergin/sync/models.py

@@ -1191,7 +1191,7 @@ def _compare_changes(
                 PushChangeType.DELETE,
                 PushChangeType.CREATE,
             ): ChangeComparisonAction.FORCE_UPDATE,
-            # delete + update = invalid sequence
+            # delete + update = replace it (used for multicheckpoint ranges when we want to keep file in history even if it was deleted in the middle, so we keep delete but update metadata and diffs)
             (
                 PushChangeType.DELETE,
                 PushChangeType.UPDATE,

server/mergin/tests/test_public_api_v2.py

@@ -496,16 +496,6 @@ def test_delta_merge_changes():
 
 def test_delta_cross_checkpoint_create_delete_recreate(client):
     """
-    Regression test for cross-checkpoint pre-merge bug: scenario 1.
-
-    A file that is created within the queried range and then deleted+re-created
-    across a rank-1 chunk boundary is silently excluded from the delta result.
-
-    Root cause: create_checkpoint calls merge_changes before storing, collapsing
-    DELETE+CREATE into CREATE and losing the DELETE. When two chunks both store
-    CREATE for the same file, the outer merge_changes in get_delta_changes sees
-    CREATE+CREATE which maps to EXCLUDE — and the file disappears from the result.
-
     Setup (rank-1 chunks cover 4 versions each, 4^1=4):
         v1–v4:  tracked.gpkg does NOT exist (client at v4 has never seen it)
         v5–v8:  tracked.gpkg is CREATED at v5  → rank-1 stores [CREATE(v5)]
@@ -549,29 +539,15 @@ def test_delta_cross_checkpoint_create_delete_recreate(client):
 
     assert delta is not None
     tracked = next((d for d in delta if d.path == "tracked.gpkg"), None)
-    assert tracked is not None, (
-        "tracked.gpkg missing from delta — cross-checkpoint pre-merge bug: "
-        "DELETE(v9)+CREATE(v10) was collapsed to CREATE inside checkpoint(v9-v12), "
-        "then CREATE(v5)+CREATE(v10) hit CREATE+CREATE→EXCLUDE in the outer merge"
-    )
+    # DELETE(v9)+CREATE(v10) was collapsed to CREATE inside checkpoint(v9-v12)
+    # then CREATE(v5)+CREATE(v10) hit CREATE+CREATE→EXCLUDE in the outer merge
+    assert tracked is not None
     assert tracked.change == PushChangeType.CREATE
     assert tracked.version == 10
 
 
 def test_delta_cross_checkpoint_recreate_then_delete(client):
     """
-    Regression test for cross-checkpoint pre-merge bug: scenario 2.
-
-    A file that existed before the queried range, is deleted+re-created within
-    chunk A, and then permanently deleted in chunk B is silently excluded from
-    the delta result instead of appearing as DELETE.
-
-    Root cause: create_checkpoint pre-merges DELETE+CREATE to CREATE in chunk A,
-    losing the DELETE. The outer merge then sees CREATE (chunk A) + DELETE (chunk B).
-    Because the stored CREATE did not populate updating_files, exclude_delete=True,
-    so CREATE+DELETE maps to EXCLUDE rather than DELETE — the file is never
-    removed from the client even though it no longer exists on the server.
-
     Setup:
         v1–v4:  base.gpkg exists (client at v4 has the file, exclude_delete should be False)
         v5–v8:  base.gpkg DELETED at v5, RE-CREATED at v6
@@ -614,12 +590,7 @@ def test_delta_cross_checkpoint_recreate_then_delete(client):
 
     assert delta is not None
     base_gpkg = next((d for d in delta if d.path == "base.gpkg"), None)
-    assert base_gpkg is not None, (
-        "base.gpkg missing from delta — cross-checkpoint pre-merge bug: "
-        "DELETE(v5)+CREATE(v6) was collapsed to CREATE inside checkpoint(v5-v8), "
-        "then CREATE(v6)+DELETE(v9) hit CREATE+DELETE with exclude_delete=True→EXCLUDE "
-        "in the outer merge, so client is never told to remove the file"
-    )
+    assert base_gpkg is not None
     assert base_gpkg.change == PushChangeType.DELETE