The actual shortening rules aren't that interesting and
probably not worth getting into (I gloss over them here as
"shortened for human readability"). But the fact that %gD
shows whatever you gave on the command line is subtle and
worth mentioning. Since most people will feed a shortened
refname in the first place, it otherwise makes it hard to
understand the difference between the two.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>