Fix porcelain.reset --hard to delete files not in target tree

When resetting to a remote branch, files that were deleted in the remote
were not being removed locally due to incorrect path normalization on
Windows. The issue was that paths were being compared with different
separators (backslash vs forward slash).

This fix normalizes paths to use forward slashes consistently, matching
Git's internal representation, ensuring files are properly deleted when
they don't exist in the target tree.

Fixes #840

NEWS

@@ -25,6 +25,11 @@
    available. The Rust implementation already raised the correct exception.
    (#1606, Jelmer Vernooij)
 
+ * Fix ``porcelain.reset --hard`` to properly delete files that don't exist in
+   the target tree. Previously, when resetting to a remote branch, files deleted
+   in the remote were not removed locally due to incorrect path normalization
+   on Windows. (#840, Jelmer Vernooij)
+
 0.23.0	2025-06-21
 
  * Add basic ``rebase`` subcommand. (Jelmer Vernooij)

dulwich/index.py

@@ -1549,6 +1549,8 @@ def update_working_tree(
                 full_path = os.path.join(root, file)
                 # Get relative path from repo root
                 rel_path = os.path.relpath(full_path, repo_path_str)
+                # Normalize to use forward slashes like Git does internally
+                rel_path = rel_path.replace(os.sep, "/")
                 rel_path_bytes = rel_path.encode()
 
                 # If this file is not in the target tree, remove it

tests/test_porcelain.py

@@ -2155,6 +2155,124 @@ class ResetTests(PorcelainTestCase):
 
         self.assertEqual([], changes)
 
+    def test_hard_deletes_untracked_files(self) -> None:
+        """Test that reset --hard deletes files that don't exist in target tree."""
+        # Create and commit a file
+        fullpath = os.path.join(self.repo.path, "foo")
+        with open(fullpath, "w") as f:
+            f.write("BAR")
+        porcelain.add(self.repo.path, paths=[fullpath])
+        sha1 = porcelain.commit(
+            self.repo.path,
+            message=b"First commit",
+            committer=b"Jane <jane@example.com>",
+            author=b"John <john@example.com>",
+        )
+
+        # Create another file and commit
+        fullpath2 = os.path.join(self.repo.path, "bar")
+        with open(fullpath2, "w") as f:
+            f.write("BAZ")
+        porcelain.add(self.repo.path, paths=[fullpath2])
+        porcelain.commit(
+            self.repo.path,
+            message=b"Second commit",
+            committer=b"Jane <jane@example.com>",
+            author=b"John <john@example.com>",
+        )
+
+        # Reset hard to first commit - this should delete 'bar'
+        porcelain.reset(self.repo, "hard", sha1)
+
+        # Check that 'foo' still exists and 'bar' is deleted
+        self.assertTrue(os.path.exists(fullpath))
+        self.assertFalse(os.path.exists(fullpath2))
+
+        # Check index matches first commit
+        index = self.repo.open_index()
+        self.assertIn(b"foo", index)
+        self.assertNotIn(b"bar", index)
+
+    def test_hard_deletes_files_in_subdirs(self) -> None:
+        """Test that reset --hard deletes files in subdirectories."""
+        # Create and commit files in subdirectory
+        subdir = os.path.join(self.repo.path, "subdir")
+        os.makedirs(subdir)
+        file1 = os.path.join(subdir, "file1")
+        file2 = os.path.join(subdir, "file2")
+
+        with open(file1, "w") as f:
+            f.write("content1")
+        with open(file2, "w") as f:
+            f.write("content2")
+
+        porcelain.add(self.repo.path, paths=[file1, file2])
+        porcelain.commit(
+            self.repo.path,
+            message=b"First commit",
+            committer=b"Jane <jane@example.com>",
+            author=b"John <john@example.com>",
+        )
+
+        # Remove one file from subdirectory and commit
+        porcelain.rm(self.repo.path, paths=[file2])
+        sha2 = porcelain.commit(
+            self.repo.path,
+            message=b"Remove file2",
+            committer=b"Jane <jane@example.com>",
+            author=b"John <john@example.com>",
+        )
+
+        # Create file2 again (untracked)
+        with open(file2, "w") as f:
+            f.write("new content")
+
+        # Reset to commit that has file2 removed - should delete untracked file2
+        porcelain.reset(self.repo, "hard", sha2)
+
+        self.assertTrue(os.path.exists(file1))
+        self.assertFalse(os.path.exists(file2))
+
+    def test_hard_reset_to_remote_branch(self) -> None:
+        """Test reset --hard to remote branch deletes local files not in remote."""
+        # Create a file and commit
+        file1 = os.path.join(self.repo.path, "file1")
+        with open(file1, "w") as f:
+            f.write("content1")
+        porcelain.add(self.repo.path, paths=[file1])
+        sha1 = porcelain.commit(
+            self.repo.path,
+            message=b"Initial commit",
+            committer=b"Jane <jane@example.com>",
+            author=b"John <john@example.com>",
+        )
+
+        # Create a "remote" ref that doesn't have additional files
+        self.repo.refs[b"refs/remotes/origin/master"] = sha1
+
+        # Add another file locally and commit
+        file2 = os.path.join(self.repo.path, "file2")
+        with open(file2, "w") as f:
+            f.write("content2")
+        porcelain.add(self.repo.path, paths=[file2])
+        porcelain.commit(
+            self.repo.path,
+            message=b"Add file2",
+            committer=b"Jane <jane@example.com>",
+            author=b"John <john@example.com>",
+        )
+
+        # Both files should exist
+        self.assertTrue(os.path.exists(file1))
+        self.assertTrue(os.path.exists(file2))
+
+        # Reset to remote branch - should delete file2
+        porcelain.reset(self.repo, "hard", b"refs/remotes/origin/master")
+
+        # file1 should exist, file2 should be deleted
+        self.assertTrue(os.path.exists(file1))
+        self.assertFalse(os.path.exists(file2))
+
 
 class ResetFileTests(PorcelainTestCase):
     def test_reset_modify_file_to_commit(self) -> None: