Optimise setup for within CERN and with CVMFS available

.gitlab-ci.yml

@@ -84,8 +84,9 @@ cmssw_addpkg:
     - cmsrel ${CMSSW_RELEASE}
     - cd ${CMSSW_RELEASE}/src
     - cmsenv
-    # For a single package analysis, the repository would be called "MyAnalysis"
-    # Here we mimick this by creating the directory by hand
+    # If within CERN, we can speed up interaction with CMSSW:
+    - export CMSSW_MIRROR=https://:@git.cern.ch/kerberos/CMSSW.git
+    - export CMSSW_GIT_REFERENCE=/cvmfs/cms.cern.ch/cmssw.git.daily
     - git cms-addpkg PhysicsTools/PatExamples
     - scram b