1) Create a remote repository to http://download.eclipse.org/jgit/maven
2) Create a virtual repository and add the remote url: http://ftp-stud.hs-esslingen.de/Mirrors/eclipse/releases/kepler/
3) When you look at the "Create or update the following repositories in Artifactory" area (see screenshot) it wants to modify the http://download.eclipse.org/jgit/maven repository to be P2 and add it because http://ftp-stud.hs-esslingen.de/Mirrors/eclipse/releases/kepler/ contains a redirect to it, but the redirect should be to http://download.eclipse.org. No way to work around this other than delete the http://download.eclipse.org/jgit/maven repository first.
Adding it as-is causes the following exception during resolution: