send-email: allow send-email to run outside a repo
send-email: allow send-email to run outside a repo

send-email is supposed to be able to run from outside a repo. This
ability was broken by commits caf0c3d6 (make the message file name more
specific) and 5df9fcf6 (interpret unknown files as revision lists).

This commit provides a fix for both.

Signed-off-by: Jay Soffian <eccf10a4397cf08f0034a6cb5e4457bdd5e3783e@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git