Comment # 7 on bug 1137913 from Petr Gajdos

Perhaps you can find some info here:
https://en.opensuse.org/openSUSE:Build_Service_Tutorial
Perhaps there is more info somewhere, perhaps you can ask on one of opensuse 
mailing lists.

Basically, we assume that most of the people use bare openSUSE 42.3, openSUSE
15.0, openSUSE 15.1, etc. You want to use software from devel project, so I
think you shift from average user level with all aspects it may have. All the
more, that you are using two packages from different devel projects that
depends one on another.

Devel projects (see the _devel_) are meant primarily for Tumbleweed
development, thus for a next distro in order. That maintainers of projects
decided to build newest software for older distributions is a voluntary service
from theirs side. They choose the name of repository by their own. And, luckily
for you, they even decided to build newest php7-imagick not only for openSUSE
15.1 as such (openSUSE_Leap_15.1), but also against newest php7 built for
openSUSE 15.1 (php_openSUSE_Leap_15.1).

In OBS, you can even have your own project, home:your_usernamename, where you
can link php php-imagick version you want from whichever project, perhaps other
packages as well, name the repository how you want, publish it and take the
benefit of download.opensuse.org by telling zypper about your own custom repo.

Of course, you can use Tumbleweed itself with the all the newest stuff.