Maybe it should be noted that "apt-get dist-upgrade" does update installed packages to the latest version, but only for the current distro-version (e.g. jessie or stretch).
To do a real upgrade to the latest distro-version and packages, you'll have to replace every occurence of the former distro-verison (like jessie) to the one you wan to update to (e.g. stretch) in /etc/apt/sources.list before executing the update and dist-upgrade.
Maybe it should be noted that "apt-get dist-upgrade" does update installed packages to the latest version, but only for the current distro-version (e.g. jessie or stretch).
To do a real upgrade to the latest distro-version and packages, you'll have to replace every occurence of the former distro-verison (like jessie) to the one you wan to update to (e.g. stretch) in /etc/apt/sources.list before executing the update and dist-upgrade.