Creation of a new Debian changelog:
   
   dch --create --package retroshare --newversion 0.6.4-1

dget command to retrieve source package:

   dget -u https://launchpad.net/~retroshare/+archive/ubuntu/stable/+files/retroshare_0.6.4-1.20180313.0e6d27ad~xenial.dsc

   (-u means don't check PGP signature)


When ready:
   * updload the package in a place that can be used to dget the package on mentors.debian.net.

   dput mentors retroshare_0.6.4-1_source.changes