Add move operation, fix fuse server

trovedb/db.py

@@ -14,6 +14,8 @@ from typing import NamedTuple
 from datetime import datetime, timezone
 from pathlib import Path
 
+from . import trove as tr
+
 NOTE_ROOT_ID = uuid.UUID(int=0)
 
 class ObjectInfo(NamedTuple):
@@ -288,13 +290,21 @@ class Sqlite3Trove:
     # Tree entry operations
     # ------------------------------------------------------------------
 
-    def link(self, parent_id: SqlObjectId, name: str, child_id: SqlObjectId) -> None:
+    def link(self, parent_id: SqlObjectId, name: str, child_id: SqlObjectId, overwrite: bool = True) -> None:
         """
         Link a child object into a tree under the given name.
-        Replaces any existing entry with the same name in this tree.
+        Replaces any existing entry with the same name in this tree if overwrite=True.
         Both parent_id and child_id must exist in the objects table
         (enforced by FK constraints).
         """
+        if not overwrite:
+            existing = self._con.execute(
+                "SELECT 1 FROM tree_entries WHERE parent_id = ? AND name = ?",
+                (_sql_id(parent_id), name),
+            ).fetchone()
+            if existing:
+                raise tr.ErrorExists(f"Entry '{name}' already exists in tree {parent_id}")
+
         self._con.execute(
             "INSERT OR REPLACE INTO tree_entries (parent_id, name, child_id) "
             "VALUES (?, ?, ?)",