policy: eliminate ".pure." from module name only if marked as dual So we can switch cext/pure modules to new layout one by one.

policy: add "cext" package which will host CPython extension modules I'm going to restructure cext/pure modules and get rid of our hgimporter hack. C extension modules will be moved to cext/ directory so old and new compiled modules can coexist in development tree. This is necessary to run 'hg bisect' without recompiling. New extension modules will be loaded by an importer function: base85 = policy.importmod('base85') # select pure.base85 or cext.base85 This will also allow us to split cffi from pure modules, which is currently difficult because pure modules can't be imported by name.

policy: mark all string literals as sysstr or bytes The policy module won't be imported early in future, which means string literals will be processed by our Python 3 loader.

debuginstall: check C extensions only if they are loadable per policy This check is useless in pure installation and I want to make it directly import C extension modules.

osutil: proxy through util (and platform) modules (API) See the previous commit for why. Marked as API change since osutil.listdir() seems widely used in third-party extensions. The win32mbcs extension is updated to wrap both util. and windows. aliases.

win32mbcs: wrap underlying pycompat.bytestr to use checkwinfilename safely win32mbcs wraps some functions, to prevent them from unintentionally treating backslash (0x5c), which is used as the second or later byte of multi bytes characters by problematic encodings, as a path component delimiter on Windows platform. This wrapping assumes that wrapped functions can safely accept unicode string arguments. Unfortunately, d1937bdcee8c broke this assumption by introducing pycompat.bytestr() into util.checkwinfilename() for py3 support. After that, wrapped checkwinfilename() always fails for non-ASCII filename at pycompat.bytestr() invocation. This patch wraps underlying pycompat.bytestr() function to use util.checkwinfilename() safely. To avoid similar regression in the future, another patch series will add smoke testing on default branch.

hghave: prefill more version of Mercurial The previous code was unable to go above version 4.0.

graft: fix graft across merges of duplicates of grafted changes Graft used findmissingrevs to find the candidates for graft duplicates in the destination. That function operates with the constraint: 1. N is an ancestor of some node in 'heads' 2. N is not an ancestor of any node in 'common' For our purpose, we do however have to work correctly in cases where the graft set has multiple roots or where merges between graft ranges are skipped. The only changesets we can be sure doesn't have ancestors that are grafts of any changeset in the graftset, are the ones that are common ancestors of *all* changesets in the graftset. We thus need: 2. N is not an ancestor of all nodes in 'common' This change will graft more correctly, but it will also in some cases make graft slower by making it search through a bigger and unnecessary large sets of changes to find duplicates. In the general case of grafting individual or linear sets, we do the same amount of work as before.

graft: test coverage of grafts and how merges can break duplicate detection This demonstrates unfortunate behaviour: extending the graft range cause the graft to behave differently. When the graft range includes a merge, we fail to detect duplicates that are ancestors of the merge.

mpatch: proxy through mdiff module See the previous commit for why.