When doing 'git rebase --autostash <upstream> <master>' with a dirty worktree
a 'HEAD is now at ...' message is emitted, which is pointless as it refers to
the old active branch which isn't actually moved.
This commit removes the 'HEAD is now at...' message.
Signed-off-by: Ben Wijen <ben@wijen.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>