patch: make extract() a context manager (API) Previously, this function was creating a temporary file and relying on callers to unlink it. Yuck. We convert the function to a context manager and tie the lifetime of the temporary file to that of the context manager. This changed indentation not only from the context manager, but also from the elination of try blocks. It was just easier to split the heart of extract() into its own function. The single consumer of this function has been refactored to use it as a context manager. Code for cleaning up the file in tryimportone() has also been removed. .. api:: ``patch.extract()`` is now a context manager. Callers no longer have to worry about deleting the temporary file it creates, as the file is tied to the lifetime of the context manager. Differential Revision: https://phab.mercurial-scm.org/D3306