How Come I Cannot Download the Latest Ubuntu 15.04 Desktop?

Sat Aug 8 11:35:30 UTC 2015

On 8/8/2015 4:25 AM, Oliver Grawert wrote:
> to change that settings, open the software-properties from your system
> settings and in the "Updates" tab use the most bottom option ("Notify me
> of a new Ubuntu version:") to enable "For any new version" ... then
> update-manager or do-release-update will allow you to upgrade to 15.04.
>

Just out of curiosity, how do I do this from the terminal?  I read the 
do-release-upgrade man page but it didn't say anything about this.  I can 
manually edit my sources.list, but am I correct in thinking this is probably 
not a good idea?