Eclipse plugins can be installed from the command line without UI. That method allows to automate the installation process and is really useful when you want to repeat the installation several times (e.g. install plugin on many workstations).
./eclipse -nosplash -application org.eclipse.equinox.p2.director -repository http://update.atlassian.com/atlassian-eclipse-plugin/rest/nightly/e3.7 -installIU com.atlassian.connector.eclipse.feature.group
More details on the available options can be found on the Eclipse knowledge base pages: http://help.eclipse.org/juno/index.jsp?topic=/org.eclipse.platform.doc.isv/guide/p2_director.html
Add the following URL to your Eclipse update sites: