phases: rename variable used for owned dict of phasesets The phaseroots variable is used for two different objects: borrowed set and owned dict of sets. It's hard to track which object should have to be decrefed on error return.

phases: leverage Py_BuildValue() to build PyInt and steal PyObject "N" means "O" without incref, so we can just return the created tuple.

phases: make sure an exception should be set on error return This should never happen, but the code looks wrong without PyErr_Set*() call.

phases: fix clang-format error

phases: fix error return with no exception from computephases() PySet_Check() does not set an exception.

osutil: fix excessive decref on tuple creation failure in listdir() The stat object would be freed on error for the same reason as the previous patch. makestat() can be inlined, but this patch doesn't change it. https://github.com/python/cpython/blob/2.7/Python/modsupport.c#L292 The __APPLE__ code is untested.

revlog: fix excessive decref on tuple creation failure in parse_index2() Since Py_BuildValue() steals the ownership of "N" arguments, these objects would already be freed if Py_BuildValue() returned NULL. https://github.com/python/cpython/blob/2.7/Python/modsupport.c#L292