When pasting an entry into jabref, check whether key already exists

[ilippert]

Is your suggestion for improvement related to a problem? Please describe.
When I paste an entry into JabRef, I occasionally mess up my library because an entry with that citation key already exists.

Describe the solution you'd like
JabRef should notify me when I paste an entry and an entry with the same key already exists. I think this already happens as part of the import function, but not when an entry is pasted.

[Siedlerchr]

Only works if you copy + paste the article twice

[koppor]

The cause is probably our duplicate check. We need to work on checking the bibtex keys when pasting...

@Article{Kopp2015,
  author    = {Kopp, Oliver and Martin, Daniel and Wutke, Daniel and Leyman, Frank},
  journal   = {Enterprise Modelling and Information Systems Architectures},
  title     = {The Difference Between Graph-Based and Block-Structured Business Process Modelling Languages},
  year      = {2015},
  pages     = {No 1 (2009)},
  volume    = {Vol 4},
  doi       = {10.18417/EMISA.4.1.1},
  language  = {en},
  publisher = {Gesellschaft für Informatik e.V. (The German Informatics Society)},
}

@Article{Kopp2015,
  author    = {Kopp},
  year = {2015},
}

[koppor]

The issue is fixed when automatic key generation is in place --> JabRef automatically detects duplicate entry; if no duplicate, the key is generated to be unique

We need to check the behavior if existing keys should not be overwritten