aptly graph specific output filename
aptly graph specific output filename

	https://github.com/smira/aptly/issues/241

	modify：     cmd/graph.go

Signed-off-by: Zhang, Guodong <fa3070971ac801a3158c660396602bcf0c29bf4b@linx-info.com>

smira/aptly,scalp42/aptly,adfinis-forks/aptly,bsundsrud/aptly,sobczyk/aptly,vincentbernat/aptly,adfinis-forks/aptly,gearmover/aptly,seaninspace/aptly,bankonme/aptly,ceocoder/aptly,scalp42/aptly,gdbdzgd/aptly,neolynx/aptly,gearmover/aptly,gearmover/aptly,sobczyk/aptly,bsundsrud/aptly,jola5/aptly,bankonme/aptly,neolynx/aptly,aptly-dev/aptly,gdbdzgd/aptly,seaninspace/aptly,ceocoder/aptly,smira/aptly,jola5/aptly,adfinis-forks/aptly,gdbdzgd/aptly,aptly-dev/aptly,vincentbernat/aptly,seaninspace/aptly,smira/aptly,neolynx/aptly,jola5/aptly,bankonme/aptly,sobczyk/aptly,scalp42/aptly,bsundsrud/aptly,vincentbernat/aptly,ceocoder/aptly,aptly-dev/aptly