@sophiewigmore In the initial change, the mirror url was not properly constructed and did not include the actual dependency archive. For instance, with the following:
original: https://artifacts.paketo.io/nginx_1.24.0_linux_x64_jammy_fa1dfe46.tgz
mirror: https://user:[email protected]/buildpacks-dependencies
...it would not append the actual tgz file to be downloaded. The result instead was https://user:[email protected]/buildpacks-dependencies/artifacts.paketo.io
This also happened with special hostnames:
original: https://github.com/nginx/nginx_1.24.0_linux_x64_jammy_fa1dfe46.tgz
mirror: https://mirror.example.org/public-github
...the result would incorrectly be https://mirror.example.org/public-github when it should be https://mirror.example.org/public-github/nginx/nginx_1.24.0_linux_x64_jammy_fa1dfe46.tgz

The initial change only worked correctly if the {originalHost} placeholder was used. This is due to line 35 of dependency_mirror.go. The path needed to be moved outside of the substitution.

I also updated the tests because the test urls did not include an appropriate scheme and path

This is helpful info! thank you