I find a dependency to org.eclipse.ui from the org.eclipse.egit.core. Looking closer I see that some operations
implement the IRunnableWithProgress interface from jface.
Since this makes it hard to use the egit.core in a headless environment, I would suggest you remove that dependency and
instead wrap the affected code in an IRunnableInProgress when using it in the org.eclipse.egit.ui component. An
alternative might be to use the IWorkspaceRunnable instead and then wrap that in a IRunnableWithProgress in the UI. That
way, you free the headless part from the need of a large number of UI bundles that are never needed.