Ensure that detached HEAD does not raise when comparing branch name.

Author: buddly27

git/config.py

@@ -493,7 +493,13 @@ def _included_paths(self):
                     paths += self.items(section)
 
             elif keyword == "onbranch":
-                if fnmatch.fnmatchcase(self._repo.active_branch.name, value):
+                try:
+                    branch_name = self._repo.active_branch.name
+                except TypeError:
+                    # Ignore section if active branch cannot be retrieved.
+                    continue
+
+                if fnmatch.fnmatchcase(branch_name, value):
                     paths += self.items(section)
 
         return paths

test/test_config.py

@@ -345,6 +345,23 @@ def test_conditional_includes_from_branch_name(self, rw_dir):
             assert config._has_includes()
             assert config._included_paths() == [("path", path2)]
 
+    @with_rw_directory
+    def test_conditional_includes_from_branch_name_error(self, rw_dir):
+        # Initiate mocked repository to raise an error if HEAD is detached.
+        repo = mock.Mock()
+        type(repo).active_branch = mock.PropertyMock(side_effect=TypeError)
+
+        # Initiate config file.
+        path1 = osp.join(rw_dir, "config1")
+
+        # Ensure that config is ignored when active branch cannot be found.
+        with open(path1, "w") as stream:
+            stream.write("[includeIf \"onbranch:foo\"]\n    path=/path\n")
+
+        with GitConfigParser(path1, repo=repo) as config:
+            assert not config._has_includes()
+            assert config._included_paths() == []
+
     def test_rename(self):
         file_obj = self._to_memcache(fixture_path('git_config'))
         with GitConfigParser(file_obj, read_only=False, merge_includes=False) as cw: