Comment # 9 on bug 1187425 from Adrian Schr���ter

okay, I add also the default prefix in another element. note for the release
managers, they need manually to add the default_obs_repository_name element,
the other one will be filled automatically.

I will send a submitrequest to factory once this is deployed.

The spec file template will look like this:

...
  <installconfig>
   <defaultlang>en_US</defaultlang>
  
<default_obs_repository_name>openSUSE_Tumbleweed</default_obs_repository_name>
   <default_obs_download_url>%{_download_url}</default_obs_download_url>
...

%_download_url will be expanded to https://download.opensuse.org/repositories 
in build.opensuse.org case.

(note: this leaves still unclear cases when specific configurations for certain
projects exist or when project maintainers opted for different repository
names. I do not want to add the generic template URL here, since the correct
way to figure out the name would be to ask the OBS api.)