For users' convenience, most rebase commands can be abbreviated, e.g.
'p' instead of 'pick' and 'x' instead of 'exec'. Let's teach the
sequencer to handle those abbreviated commands just fine.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>