One of the several uses of the CircleCI CLI is to run jobs locally. However, it is currently not possible to add SSH keys using the
add_ssh_keys CLI command.
Essentially, in this case, you'll need to pass some form of credentials into the container.
You can set your VCS username/password as environment variables and pass them to the CLI with the
-e flag, for each variable. This would allow you to clone the repository with basic authentication.
Alternatively, you can base64-encode the private key and pass it into the job as an environment variable as well.
Then you can decode it into a file within a
run command in your custom local config.
Once decoded into a file you can use
ssh-add -K path/to/key. This would allow you access to the remote repository through SSH key based authentication.