I've tried to use this ppa:
sudo apt-add-repository ppa:elementary-os/daily
sudo apt-get update
but it says "Unable to locate package pantheon-files"
grep "^deb " /etc/apt/sources.list
deb http://cz.archive.ubuntu.com/ubuntu/ zesty main restricted
deb http://cz.archive.ubuntu.com/ubuntu/ zesty-updates main restricted
deb http://cz.archive.ubuntu.com/ubuntu/ zesty universe
deb http://cz.archive.ubuntu.com/ubuntu/ zesty-updates universe
deb http://cz.archive.ubuntu.com/ubuntu/ zesty multiverse
deb http://cz.archive.ubuntu.com/ubuntu/ zesty-updates multiverse
deb http://cz.archive.ubuntu.com/ubuntu/ zesty-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu zesty-security main restricted
deb http://security.ubuntu.com/ubuntu zesty-security universe
deb http://security.ubuntu.com/ubuntu zesty-security multiverse
And
apt policy pantheon-files
N: Unable to locate package pantheon-files
apt policy pantheon-files
? add it to your question. – Ravexina Jul 01 '17 at 20:49grep "^deb " /etc/apt/sources.list
? – Ravexina Jul 01 '17 at 20:51