Arch Linux / makepkg: rel is always set 0

[Letterus]

This service/script always sets "rel" to zero instead of reading it from pkgbuild file or the source service.

_replace_tag(filename, "pkgrel", "0")

This somewhat breaks Arch Linux packaging, because on updating a package I now have to update the version number of the source while it should only be the number of "rel".

Best would be if it would read this number from pkbuild file and increment it as long as the version of the sources remain the same.

[portaloffreedom]

As a quick fix I would be content with setting pkgrel to the OBS revision number, it would never reset to zero, but updates would work correctly. If someone can help me understand how to get the revision number in python (reading a file? environment variable?) I can make the PR myself.

[Letterus]

Looks good to me. Pinging @M0ses for review, please.