Result inconsistency for __call__, is_ignored_file and is_ignored_dir

[karajan1001]

Bug Report

Please provide information about your setup

Output of dvc version:

$ dvc version

master

Additional Information (if any):

If applicable, please also provide a --verbose output of the command, eg: dvc add --verbose.

Now there are several interfaces for the dvcignore.
In is_ignored_dir we ignored all paths outside the repo.

dvc/dvc/ignore.py

Lines 270 to 272 in 35dd1fd

	def _is_ignored(self, path, is_dir=False):
	if self._outside_repo(path):
	return True

In a direct call __call__ all outside paths are included.

dvc/dvc/ignore.py

Lines 241 to 244 in 35dd1fd

	if ignore_pattern:
	return ignore_pattern(root, dirs, files)
	else:
	return dirs, files

And in is_ignored_files there is a bug that makes us skipped "outside the repo" check and return False forever.

dvc/dvc/ignore.py

Lines 275 to 278 in 35dd1fd

	if ignore_pattern:
	return ignore_pattern.matches(dirname, basename, is_dir)
	else:
	return False

They should be unified. So in what condition do we need to mask files outside the repo? And should we put this logic in dvcignore?