In this line, the provided PKGBUILD file is copied to /tmp/local-repo without modifying its name. This causes the subsequent steps to not work properly if the filename is not exactly "PKGBUILD" (for example, when publishing multiple packages at once). Additionally, there is no error message.

I believe this line cp -r "$pkgbuild" /tmp/local-repo/ should be changed to cp "$pkgbuild" /tmp/local-repo/PKGBUILD. This, of course, could break the workflows of those who passed a directory instead of a file in $pkgbuild and relied on the old behavior to copy its contents, but the description of the pkgbuild parameter is "Path to PKGBUILD file", which makes it clear that you should pass a single file instead of a directory, and they should be using assets instead.

I'm creating an issue instead of a PR because I'm not sure if my reasoning is correct, and maybe this breaks something else.