[merge] Repository.tarball hpss command

[John Arbash Meinel]

John Arbash Meinel has voted +1 (conditional).
Status is now: Conditionally approved
Comment:
I would rather see it avoid creating the temp repository on both sides, 
but otherwise +1. (It probably is easiest to still create the temp 
repository for the client, but the server could generate the tarball in 
memory)

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C20070416161531.GA13640%40sourcefrog.net%3E