git format-patch --in-reply-to allows header injection. Intended?

Hi,

I just wanted to ask if the --in-reply-to flag of git format-patch is supposed to write the given string unmodified into the email or whether it ought to perform some check against header injection.

For example, if you pass "--in-reply-to=<msgid>\nTo: <other@example.com"
(notice lack of trailing `>`), then the generated email will actually
contain a
  To: <other@example.com>
header.

(Depending on your shell you might also use "--in-reply-to=`cat`" to get the above working more easily.)

Is this known and working as intended, or undesired?

Thanks! Niklas