merge: check filename case collision between changesets for branch merging this patch makes branch merging abort when merged changesets have same file in different case on case insensitive filesystem. this patch does not prevent linear update which merges between target and working contexts, because 'branchmerge' is False in such case.

i18n: use encoding.lower/upper for encoding aware case folding this patch uses encoding.lower/upper for case folding, because ones of str can not fold case of non ascii characters correctly. to avoid cyclic dependency and to encapsulate logic of normcase in each platforms, this patch introduces encodinglower/encodingupper in both posix/windows specific files. this patch does not change implementation of normcase() in posix.py, because we do not know the encoding of filenames on POSIX. some "normcase()" are excluded from function wrap list in hgext/win32mbcs.py, because they become encoding aware by this patch.

windows: use upper() instead of lower() or os.path.normcase() this patch uses upper() instead of lower() or os.path.normcase() for case folding on Windows(NTFS), because lower-ing causes problems for some languages on it. see below for detail about problem of lower-ing: https://blogs.msdn.com/b/michkap/archive/2005/01/16/353873.aspx

icasefs: avoid normcase()-ing in util.fspath() for efficiency 'dirstate._normalize()', the only caller of 'util.fspath()', has already normcase()-ed path before invocation of it. normcase()-ed root can be cached on dirstate side, too. so, this patch changes 'util.fspath()' API specification to avoid normcase()-ing in it.

icasefs: use util.normcase() instead of lower() or os.path.normcase in fspath this also avoids lower()-ing on each path components by reuse the path normcase()-ed at beginning of function.

dirstate: prevent useless util.fspath() invocation for '.' at first of dirstate.walk() on case insensitive filesystem, normalization of '.' causes util.fspath() invocation, but '.' is not cached in it. this invocation is not only useless, but also harmful: initial "hg tag" causes creation of ".hgtags" file after dirstate.walk(), and looking up ".hgtags" in cache will fail, because directory contents of root is already cached at util.fspath() invocation for '.'.

icasefs: consider as case sensitive if there is no counterevidence, for safety for safety, this patch prevents case-less name from misleading into case insensitivity, even though such names should not be used.

pathauditor: switch normcase logic according to case sensitivity of filesystem this patch applies 'util.normcase()' to audit path only on case insensitive filesystem.