git-fetch-with-cli doesn't work well with custom registries #6241
Description
The git repository URLs for custom registries are currently forbidden from containing credentials. Unfortunately, that interacts poorly with the git-fetch-with-cli option since command-line git will default to using your username as the username when authenticating. However, a common configuration (e.g. with Github) is to use a single user named git for all users, so you end up with an error:
Updating crates.io index
Updating `ssh://my-git-server/my-registry-index` index
sfackler@my-git-server: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
error: failed to load source for a dependency on `some-crate`
Caused by:
Unable to update registry `ssh://my-git-server/my-registry-index`
Caused by:
failed to fetch `ssh://my-git-server/my-registry-index`
Caused by:
process didn't exit successfully: `git fetch --tags --quiet 'ssh://my-git-server/my-registry-index' 'refs/heads/master:refs/remotes/origin/master'` (exit code: 128)
Note how the Permission denied message tried sfackler@my-git-server rather than git@my-git-server which would have worked.
It seems like we should relax the restriction on credentials in custom registry configurations to only forbid passwords and not usernames.