py3: make sure we open file in bytes mode Differential Revision: https://phab.mercurial-scm.org/D3274

diffhelpers: be more tolerant for stripped empty lines of CRLF ending Exchange. It appears to trim lines containing only whitespace as well as converting LF to CRLF.

diffhelpers: make return value of testhunk() more Pythonic It's no longer C.

patch: error out if reached to EOF while reading hunk This was where out-of-bounds read occurred in old C extension.

diffhelpers: remove unused return value from fixnewline() and addlines()

diffhelpers: move out of pure package

diffhelpers: naming and whitespace cleanup

diffhelpers: remove C implementation in favor of pure Python version

patch: stop using cext.diffhelpers The C implementation has a couple of memory bugs, and lacks error handling which could lead to SEGV. I could fix them one by one (and I mostly finished that), but the performance gain provided by cext.diffhelper is quite low. Besides, diffhelpers.addlines() calls back Python, linereader.readline(), from the innermost loop. $ hg export -R mozilla-central 0:100 > patch $ ls -lh patch -rw-r--r-- 184M patch $ hg init repo && hg -R repo import patch --time --bypass (cext) time: real 34.970 secs (user 32.720+0.000 sys 2.230+0.000) (pure) time: real 35.950 secs (user 33.600+0.000 sys 2.330+0.000) So, let's simply use the pure Python implementation.

diffhelpers: port docstrings from cext to pure I'll remove the C implementation.