reachableroots: return NULL if we're throwing an exception Based on my reading of [0] and surrounding sections, if we want an exception to be properly raised when something goes wrong in the C code, we need to make sure we return NULL here. Do so. https://docs.python.org/2/extending/extending.html#back-to-the-example

reachableroots: fix transposition of set and list types in PyArg_ParseTuple This is being masked by the function not properly returning NULL when it raises an exception, so the client code was just falling back to the native codepath when it got None back. A future change removes all reason for this C function to return None, which exposed this problem during development.

reachableroots: consistently use short-form of PyErr_NoMemory()

reachableroots: if allocating a new set fails, use PyErr_NoMemory() My inspection of the implementation of PySet_New() indicates that it does *not* reliably set an exception in the cases where it returns NULL (as far as I can tell it'll never do that!), so let's set that up ourselves.

reachableroots: default to the C implementation This patch is part of a series of patches to speed up the computation of revset.reachableroots by introducing a C implementation. The main motivation is to speed up smartlog on big repositories. At the end of the series, on our big repositories the computation of reachableroots is 10-50x faster and smartlog on is 2x-5x faster. Before this patch, reachableroots was computed in pure Python by default. This patch makes the C implementation the default and provides a speedup for reachableroots.

changelog: add way to call the reachableroots C implementation This patch is part of a series of patches to speed up the computation of revset.reachableroots by introducing a C implementation. The main motivation is to speed up smartlog on big repositories. At the end of the series, on our big repositories the computation of reachableroots is 10-50x faster and smartlog on is 2x-5x faster. This patch allows us to call the new C implementation of reachableroots from python by creating an entry point in the changelog class.