i18n: use UTF-8 string to lower filename for case collision check

Some character sets, cp932 (known as Shift-JIS for Japanese) for
example, use 0x41('A') - 0x5A('Z') and 0x61('a') - 0x7A('z') as second
or later character.

In such character set, case collision checking recognizes different
files as CASEFOLDED same file, if filenames are treated as byte
sequence.

win32mbcs extension is not appropriate to handle this problem, because
this problem can occur on other than Windows platform only if
problematic character set is used.

Callers of util.checkcase() use known ASCII filenames as last
component of path, and string.lower() is not applied to directory part
of path. So, util.checkcase() is kept intact, even though it applies
string.lower() to filenames.

tests/test-casecollision-i18n.t

@@ -0,0 +1,43 b''
+run only on case-insensitive filesystems, because collision check at
+"hg update" is done only on case-insensitive filesystems
+
+  $ "$TESTDIR/hghave" icasefs || exit 80
+
+setup repository, and target files
+
+  $ HGENCODING=cp932
+  $ export HGENCODING
+  $ hg init t
+  $ cd t
+  $ python << EOF
+  > names = ["\x83\x41", # cp932(0x83, 0x41='A'), UNICODE(0x30a2)
+  >          "\x83\x5A", # cp932(0x83, 0x5A='Z'), UNICODE(0x30bb)
+  >          "\x83\x61", # cp932(0x83, 0x61='a'), UNICODE(0x30c2)
+  >          "\x83\x7A", # cp932(0x83, 0x7A='z'), UNICODE(0x30db)
+  >         ]
+  > for num, name in zip(range(len(names)), names):
+  >     # file for getting target filename of "hg add"
+  >     f = file(str(num), 'w'); f.write(name); f.close()
+  >     # target file of "hg add"
+  >     f = file(name, 'w'); f.write(name); f.close()
+  > EOF
+
+test filename collison check at "hg add"
+
+  $ hg add --config ui.portablefilenames=abort `cat 0`
+  $ hg add --config ui.portablefilenames=abort `cat 1`
+  $ hg add --config ui.portablefilenames=abort `cat 2`
+  $ hg add --config ui.portablefilenames=abort `cat 3`
+  $ hg status -a
+  A \x83A (esc)
+  A \x83Z (esc)
+  A \x83a (esc)
+  A \x83z (esc)
+
+test filename collision check at "hg update"
+
+  $ hg commit -m 'revision 0'
+  $ hg update null
+  0 files updated, 0 files merged, 4 files removed, 0 files unresolved
+  $ hg update tip
+  4 files updated, 0 files merged, 0 files removed, 0 files unresolved

mercurial/merge.py

@@ -7,7 +7,7 b''
 
 from node import nullid, nullrev, hex, bin
 from i18n import _
-import scmutil, util, filemerge, copies, subrepo
+import scmutil, util, filemerge, copies, subrepo, encoding
 import errno, os, shutil
 
 class mergestate(object):
@@ -92,7 +92,7 b' def _checkcollision(mctx):'
     "check for case folding collisions in the destination context"
     folded = {}
     for fn in mctx:
-        fold = fn.lower()
+        fold = encoding.lower(fn)
         if fold in folded:
             raise util.Abort(_("case-folding collision between %s and %s")
                              % (fn, folded[fold]))

mercurial/scmutil.py

@@ -6,7 +6,7 b''
 # GNU General Public License version 2 or any later version.
 
 from i18n import _
-import util, error, osutil, revset, similar
+import util, error, osutil, revset, similar, encoding
 import match as matchmod
 import os, errno, re, stat, sys, glob
 
@@ -46,10 +46,10 b' class casecollisionauditor(object):'
         self._abort = abort
         self._map = {}
         for f in existingiter:
-            self._map[f.lower()] = f
+            self._map[encoding.lower(f)] = f
 
     def __call__(self, f):
-        fl = f.lower()
+        fl = encoding.lower(f)
         map = self._map
         if fl in map and map[fl] != f:
             msg = _('possible case-folding collision for %s') % f