Prevent clean files from showing up as untracked

Looking at the code in porcelain.path_to_tree_path,
this looks like there was an attempt at this in
85b5383, however
relpath is non-destructive, and has no effect unless
the result is assigned to something. If this were
assigned when path is relative, then relpath would
assume path was at root, and so we must check that
the path is absolute before calling relpath.

Fixes jelmer#598

dulwich/porcelain.py

@@ -168,11 +168,12 @@ def open_repo_closing(path_or_repo):
 def path_to_tree_path(repopath, path):
     """Convert a path to a path usable in e.g. an index.
 
-    :param repo: Repository
+    :param repopath: Repository
     :param path: A path
     :return: A path formatted for use in e.g. an index
     """
-    os.path.relpath(path, repopath)
+    if os.path.isabs(path):
+        path = os.path.relpath(path, repopath)
     if os.path.sep != '/':
         path = path.replace(os.path.sep, '/')
     return path.encode(sys.getfilesystemencoding())

dulwich/tests/test_porcelain.py

@@ -796,17 +796,27 @@ def test_empty(self):
             results.staged)
         self.assertEqual([], results.unstaged)
 
-    def test_status(self):
-        """Integration test for `status` functionality."""
+    def commit_file(self, name, content='original', author=b'', committer=b''):
+        fullpath = os.path.join(self.repo.path, name)
 
-        # Commit a dummy file then modify it
-        fullpath = os.path.join(self.repo.path, 'foo')
         with open(fullpath, 'w') as f:
-            f.write('origstuff')
+            f.write(content)
 
         porcelain.add(repo=self.repo.path, paths=[fullpath])
-        porcelain.commit(repo=self.repo.path, message=b'test status',
-                         author=b'', committer=b'')
+        porcelain.commit(
+            repo=self.repo.path,
+            message=u'Add {}'.format(name).encode('utf-8'),
+            author=author,
+            committer=committer,
+        )
+
+        return fullpath
+
+    def test_status(self):
+        """Integration test for `status` functionality."""
+
+        # Commit a dummy file then modify it
+        fullpath = self.commit_file('foo')
 
         # modify access and modify time of path
         os.utime(fullpath, (0, 0))
@@ -827,6 +837,21 @@ def test_status(self):
                          filename_add.encode('ascii'))
         self.assertEqual(results.unstaged, [b'foo'])
 
+    def test_status_clean(self):
+        """Integration test for `status` functionality."""
+
+        self.commit_file('foo')
+
+        results = porcelain.status(self.repo)
+
+        self.assertEqual(results.staged, {
+            'add': [],
+            'delete': [],
+            'modify': [],
+        })
+        self.assertEqual(results.unstaged, [])
+        self.assertEqual(results.untracked, [])
+
     def test_get_tree_changes_add(self):
         """Unit test for get_tree_changes add."""