Due to misuse of argparse in commit 82492f5d76
it was impossible to use both --datadirs and extra args passed directly
to msgfmt at the same time.
I'm not sure anyone actually knows how argparse works, so misusing it is
easy. What is definitely known is that argparse is NOT a POSIX compliant
parser and doesn't behave the way you'd expect a standards based parser
to handle options. Instead it caters to the easy use case, and hopes and
prays you don't need to do anything too complicated "with the wrong kind
of complicated".
Apparently, this particular type of complicated is when you have mixed
option_arguments and operands while simultaneously passing some operands
as nargs after a --.
It totally breaks, and interprets --datadirs, which is supposed to be an
option_argument, as an operand, eats it up as a msgfmt wrapped argument,
and breaks.
But if you don't pass additional arguments with -- then it interprets
--datadirs after operands as an option_argument. This is what we were
doing.
Instead pass option_arguments before all operands (including the ones
specified via `-- ...`). Add test case to pass meaningless datadirs (we
don't actually care if $GETTEXTDATADIRS is set to something that doesn't
contain gettext data).
e67fd1f551