Using tsrc with GitLab CI

[dmerejkowsky]

Today you have two options.

• Deploy a ssh key on all the runners
• Patch the manifest to replace git@gitlab.instance URLs with https://gitlab-ci-token:${CI_JOB_TOKEN}@gitlab.instance and use --no-update-manifest option when running sync - See #275

Both are not ideal. Let's see if we can find better solutions!

[dmerejkowsky]

We could also update the documentation. See also #238

[dmerejkowsky]

Well, looks like we have a workaround now: #338. Thanks @Lecrapouille :)