Suggestion: Prefer local patch files over URLs
The vast majority of patches defined in modulesets are hosted directly in the gtk-osx repo: instead of downloading said patches from the internet on build, is there a reason the local files from the git clone are not used directly instead?
This already works by default: if I do a find-and-replace of the URLS with this repo's URL prefix to leave just the filename, patches are applied from the clone correctly.
The current approach also has the disadvantage that branches tracking older versions may end up with dead links to patches since the URLs are for master specifically, and patches may get removed in master while they would still be needed for an older branch. Using local files would therefore allow to not rely on such links becoming unavailable in the future.
By the way, thanks for the awesome work on gtk-osx, it's a great project!