revlog: implement fast_rank retrieval in C This will be useful in particular to avoid going through the Python interpreter in native Rust functions. Differential Revision: https://phab.mercurial-scm.org/D12209

revlog: return 0 for the fast_rank of nullrev By convention, the rank of the null revision is 0. This particular revision is never "physically" stored in the changelog, so it is a special case. For consistency, the value `None` is still being returned for revlogs which do not store the fast_rank property for any revision. Differential Revision: https://phab.mercurial-scm.org/D12208

setup: drop support for Python 3.5 We talked about this on the mailing list [1] and there seemed to be agreement that Python 3.5 is effectively dead and no longer worth supporting. So this commit changes our minimum version requirement to 3.6.2. [1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2022-February/147885.html Differential Revision: https://phab.mercurial-scm.org/D12315

packaging: remove requirements constraints to support Python 2 We just deleted support for Python 2 from the packaging code. We no longer need these package constraints in the requirements file to support Python 2. Differential Revision: https://phab.mercurial-scm.org/D12267