Comment 2 for bug 1980982

You can encode user/pw in the URL that you fetch.
Maybe you can try with this one first?

git fetch --dry-run https://none:<email address hidden>/~ahasenack/ubuntu/+source/amavisd-new refs/heads/merge-lp1946841-jammy
remote: Authorisation required.
fatal: Authentication failed for 'https://git.launchpad.net/~ahasenack/ubuntu/+source/amavisd-new/'

The only problem is that you probably want to separate those really asking for auth from those just failing because we are using a fake user. But it might be a step forward as it does not hang.