Update README.md

README.md

@@ -6,15 +6,16 @@ be available either locally or via cvmfs!
 
 Clone respository with submodules:
 ```
-git clone --recursive https://gitlab.ekp.kit.edu/qcd-public/law-analysis.git
+git clone --recursive https://gitlab.etp.kit.edu/qcd-public/law-analysis.git --branch master
 ```
 or
 ```
-git clone --recursive git@gitlab.ekp.kit.edu:qcd-public/law-analysis.git
+git clone --recursive git@gitlab.etp.kit.edu:qcd-public/law-analysis.git --branch master
 ```
-If you get an error message from git like:
-"warning: remote HEAD refers to nonexistent ref, unable to checkout."
-then start over and try adding "--branch master" to the checkout command line.
+The "--branch master" is necessary to avoid warnings like:
+"warning: remote HEAD refers to nonexistent ref, unable to checkout.",
+after which effectively nothing is properly cloned and needs to be re-cloned
+into a new directory.
 
 Copy example config from setup/configs to ./luigi.cfg
 Copy example NNLOJET runcard [name].run from setup/runcards to .