I use the same command line since at least 8 years to create tarballs (tar cvjf plop.tar.bz2 plop/), I know it by heart, I do not need to think. If you want me to change my habits, at least give me the solution (it seems you have), otherwise I will not make the effort.

tar cvJf plop.tar.xz plop/

BTW I'm not interested in any personal habits here, I'd just like to point out that if the commands for recreating the tarballs would be documented in the specfile (or even better, included as a separate runnable script) as noted in the packaging guidelines, nobody would have to remember them:
https://fedoraproject.org/wiki/Packaging:SourceURL#Using_Revision_Control

(In reply to Ville Skyttä from comment #2)
> tar cvJf plop.tar.xz plop/

I didn't think the fix was so easy... Sorry.

This bug appears to have been reported against 'rawhide' during the Fedora 20 development cycle.
Changing version to '20'.

More information and reason for this action is here:
https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora20

This package has changed ownership in the Fedora Package Database.  Reassigning to the new owner of this component.

Hi Ville.

I'm the new component owner. I wanted to update all the sources and compress them with xz, but unfortunately one of the sources cannot be pulled from the server and I need to report that and get some help. Hopefully I'll get the upstream response soon.

Will inform you about news.

Thanks for the report.

Regards,
Jaromir.

Hi Ville.

I'm building the latest revisions of all kicad components right now. All the tarballs are compressed with the xz tool. So, considering this resolved and closing.

Regards,
Jaromir.