The existing package for the elementary Dark theme, aptly named elementary-dark-theme, is... really bad. It downloads the source archive over HTTP instead of HTTPS, doesn't use checksums to verify the download, gives the wrong source URL and license... So I put up elementary-dark, and filed a request to replace ("merge") the old package with the new one. After doing a lot of work with Debian packaging in the past, I was pleasantly surprised by how easy the PKGBUILD format is to work with.