Some git providers, such as AWS CodeCommit, require an SSH username to clone repositories. By default, Bitrise chooses the system user, which is vagrant.

In this case, the best way to make sure the correct username is used is to update the ssh URL in your .gitmodules to include the required username.

You can set this up initially by doing the following:

cd required-submodule git remote set-url origin newuser@server:/repopath

If you need to change this down the road you can do so by doing the following:

git config submodule.required-submodule.url newuser@server:/repopath