py3: document why os.fsencode() can be used to get back bytes argv
And a possible Windows issue. I'm sad we have to do such ugly hack, but
that's the unicode on Python 3.
--- a/mercurial/pycompat.py Wed Nov 09 22:15:51 2016 +0900
+++ b/mercurial/pycompat.py Wed Nov 09 22:06:09 2016 +0900
@@ -43,6 +43,14 @@
osname = os.name.encode('ascii')
ospathsep = os.pathsep.encode('ascii')
ossep = os.sep.encode('ascii')
+
+ # Since Python 3 converts argv to wchar_t type by Py_DecodeLocale() on Unix,
+ # we can use os.fsencode() to get back bytes argv.
+ #
+ # https://hg.python.org/cpython/file/v3.5.1/Programs/python.c#l55
+ #
+ # TODO: On Windows, the native argv is wchar_t, so we'll need a different
+ # workaround to simulate the Python 2 (i.e. ANSI Win32 API) behavior.
sysargv = list(map(os.fsencode, sys.argv))
def sysstr(s):