rev-list --boundary

With the new --boundary flag, the output from rev-list includes
the UNINTERESING commits at the boundary, which are usually not
shown.  Their object names are prefixed with '-'.

For example, with this graph:

              C side
             /
	A---B---D master

You would get something like this:

	$ git rev-list --boundary --header --parents side..master
	D B
        tree D^{tree}
        parent B
        ... log message for commit D here ...
        \0-B A
        tree B^{tree}
        parent A
        ... log message for commit B here ...
        \0

Signed-off-by: Junio C Hamano <junkio@cox.net>