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/etc/apt/sources.list.d/jcfp-ppa-trusty.list:deb http://ppa.launchpad.net/jcfp/ppa/ubuntu trusty main
I like it the current way (it makes testing an automatic process), but I wonder about situations where people only want the 'official' releases. If so, a separate PPA-main and PPA-testing/-rc could fullfill both needs. FWIW: I don't know how much work that is.
Indeed the ppa tends to track public releases, betas and rcs included, as a reasonable trade-off (imho) in terms of features, bugs, increased testing, and stability. After all, sab releases introducing larger code changes tend to have private pre-releases of some kind. Those with overwhelming focus on stability really shouldn't ever be auto-updating any program without requiring specific features or bug fixes.
Technically a "finals-only" is easy enough though, all it takes is a re-upload of an existing source package to an extra repository or copying packages from one ppa to another in launchpad. Just never saw the need.