The '-o' option is commonly used in many tools to specify the output file.
Typing '--output' every time is a bit too long to be a practical alternative
to redirecting output. But specifying the output name has the advantage of
making possible to guess the desired output format by filename extension.
Signed-off-by: Dmitry Potapov <dpotapov@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>