index: don't include nullid in the internal "length" field This is a follow-up to 781b2720d2ac (index: don't include nullid in len(), 2018-07-20). I intentionally didn't update the "index stats", so it will also not include the space for nullid after this patch. Differential Revision: https://phab.mercurial-scm.org/D4162

tests: add test coverage for revlogindex[-1] which was previously missing Differential Revision: https://phab.mercurial-scm.org/D4184

context: safegaurd from 'lx' being passed as file flag in manifest Follows up for d558e53cd6b619d5f671a7580513bfc66a398eac. Differential Revision: https://phab.mercurial-scm.org/D4259

debugcommands: urlerror only has a read() method in Python 2 Differential Revision: https://phab.mercurial-scm.org/D4258

debugcommands: get_method should always return a sysstr Differential Revision: https://phab.mercurial-scm.org/D4257

stringutil: if we get a memoryview in escapestr, coerce it to bytes Otherwise we get an exception. Sadly, this manifesting deep inside the wireproto code, inside a future. For some reason the exception was /causing a hang/ rather than actually propagating out, which seems like it might merit some investigation in the future. Differential Revision: https://phab.mercurial-scm.org/D4256