merge.pl decoupled from MG5

[agrohsje]

Dear @menglu21, @bbilin , @colizz, @sihyunjeon ,

I realized a potential problem.
In gridpack_generation.sh, we are copying merge.pl to our working path from
https://github.com/cms-sw/genproductions/blob/master/bin/MadGraph5_aMCatNLO/Utilities/merge.pl.
This code is no longer in sync with what is used by MG5. See e.g. this bug fix by Olivier:
https://bazaar.launchpad.net/~maddevelopers/mg5amcnlo/LTS_dev/revision/377
On top, I think we have a python version adapted by @colizz of that code:
https://github.com/cms-sw/cmssw/blob/master/GeneratorInterface/LHEInterface/scripts/mergeLHE.py
which is also not synced.
Questions: Shouldn't we monitor potential changes to this code by the MG5 authors and migrate them to our versions?

I also spotted that we keep a second (not used?) version in genproductions:
https://raw.githubusercontent.com/cms-sw/genproductions/master/Utilities/scripts/merge.pl
If I am right that it is not used, I would suggest to delete.

Cheers, Alexander.

[sihyunjeon]

so in the end this was relevant to the pnr issue! at least we could've been safe from the perl issue if i listened to you carefully :| i think we can migrate to the python version once we test all the corner cases