Retry on failed merge request with external CI (Jenkins)

I've set up GitLab 8.4 to communicate with Jenkins 1.648 with the GitLab Plugin 1.1.28. GitLab properly triggers builds on Jenkins when a merge request is submitted and retrieves the result. This is great!

In some cases, I would like to retry a build. There are tons of reasons that would require that (typically, a build slave went off and the build is considered a failure).

Searching a little bit, I've heard that when linked with GitLab CI, GitLab CE shows a "Retry" button on the build page. Could this be possible to add this for external CI system?

Does this feature involve anything else than basically just sending the HTTP request again?