What are the ways to merge packages with the same name from multiple Oracle databases?

Question

Oracle

At work, a task suddenly fell down that I had no relation to before (I'm not an oraclist):
The developers were developing in the Oracle DBMS on several bases / layouts at the same time. Moreover, the same packages could change on several bases. Now we need to assemble a single reference database from all this chaos. What can you advise reliable and convenient ways to do this?
Development is carried out on pl/sql developer and sql developer.
Bonus questions: how to avoid this chaos in the future? Source storage in SVN? And how to organize it correctly? What is the best way to organize the hit of versions from developers on the reference database and the hit of scripts from the reference database on combat bases?