posixfile_nt: '+' was understood as read mode instead of update.

mercurial/util_win32.py

@@ -209,9 +209,9 b' class posixfile_nt(object):'
 
     def __init__(self, name, mode='rb'):
         access = 0
-        if 'r' in mode or '+' in mode:
+        if 'r' in mode:
             access |= win32file.GENERIC_READ
-        if 'w' in mode or 'a' in mode:
+        if 'w' in mode or 'a' in mode or '+' in mode:
             access |= win32file.GENERIC_WRITE
         if 'r' in mode:
             creation = win32file.OPEN_EXISTING