Do not embed git credentials in git clone config
Both in the pipeline and in various git repo -> tarball scripts in cki-tools and kernel-webhooks, git repos are cloned with authorization embedded into the git repo URL. This causes the URL to be embedded in the git config file, which makes the rotation of the access tokens impossible.
AC:
- use something like https://git-scm.com/docs/git-credential-store to provide credentials instead of embedding them in the URL