help: adding a help category to narrow and remotefilelog commands Differential Revision: https://phab.mercurial-scm.org/D6998

rust-cpython: drop self.borrow_mut() in favor of PySharedRef wrapper

rust-cpython: drop self.leak_immutable() in favor of PySharedRef wrapper

rust-cpython: add safe wrapper representing shared data borrowed from PyObject PySharedRef is a tempoary wrapper around PySharedRefCell. It provides safe functions for each shared data. $shared_accessor implements a safe method to construct PySharedRefCell. This allows us to add more than once PySharedRefCell to a Python object.

rust-cpython: move $leaked struct out of macro It wasn't easy to hack the $leaked struct since errors in macro would generate lots of compile errors. Let's make it a plain struct so we can easily extend it. PyLeakedRef keeps a more generic PyObject instead of the $name struct since it no longer has to call any specific methods implemented by the $name class. $leaked parameter in py_shared_iterator!() is kept for future change.

rust-cpython: store leaked reference to PySharedState in $leaked struct I want to move it out of the macro, and allow multiple sharable objects per PyObject.

rust-cpython: mark PySharedState as Sync so &'PySharedState can be Send The goal is to store &'static PySharedState in $leaked struct, which allows us to move the $leaked struct out of the macro. Currently, it depends on inner.$data_member(py), which can't be generalized. PySharedState is Sync because any mutation or read operation is synchronized by the Python GIL, py: Python<'a>, which should guarantee that &'PySharedState can be sent to another thread.