Overwrite existing dest entries when merge_tree copies a symlink

path/__init__.py

@@ -1662,8 +1662,12 @@ def ignored(item: Self) -> bool:
         for source in itertools.filterfalse(ignored, sources):
             dest = dst_path / source.name
             if symlinks and source.islink():
-                target = source.readlink()
-                target.symlink(dest)
+                # copy2 overwrites files; replace dest so a re-merge does not fail
+                if dest.islink() or dest.is_file():
+                    dest.remove()
+                elif dest.is_dir():
+                    dest.rmtree()
+                source.readlink().symlink(dest)
             elif source.is_dir():
                 source.merge_tree(
                     dest,

tests/test_path.py

@@ -919,6 +919,39 @@ def test_with_nonexisting_dst_args(self):
         assert set(self.subdir_b.iterdir()) == expected
         self.check_link()
 
+    def test_overwrite_existing_symlink(self):
+        """
+        Re-merging a tree that contains symlinks should overwrite
+        destination links instead of raising FileExistsError.
+        """
+        self.subdir_a.merge_tree(self.subdir_b, True)
+        self.subdir_a.merge_tree(self.subdir_b, True)
+        self.check_link()
+
+    def test_overwrite_retargets_existing_symlink(self):
+        self.subdir_a.merge_tree(self.subdir_b, True)
+        self.test_link.remove()
+        other = self.subdir_a / 'other.txt'
+        other.write_text('y', encoding='utf-8')
+        other.symlink(self.test_link)
+        self.subdir_a.merge_tree(self.subdir_b, True)
+        dest_link = self.subdir_b / self.test_link.name
+        assert dest_link.islink()
+        assert dest_link.readlink().basename() == other.name
+
+    def test_symlink_replaces_existing_file(self):
+        dest_link = self.subdir_b / self.test_link.name
+        dest_link.write_text('not a link', encoding='utf-8')
+        self.subdir_a.merge_tree(self.subdir_b, True)
+        assert dest_link.islink()
+
+    def test_symlink_replaces_existing_directory(self):
+        dest_link = self.subdir_b / self.test_link.name
+        dest_link.mkdir()
+        (dest_link / 'child').touch()
+        self.subdir_a.merge_tree(self.subdir_b, True)
+        assert dest_link.islink()
+
     def test_with_existing_dst(self):
         self.subdir_b.rmtree()
         self.subdir_a.copytree(self.subdir_b, True)