working on a spark SQL and mongodb project at Intellectdesign. this is the URL I refer to
https://github.com/mongodb/mongo-spark
when ./sbt +publish-signed, it ask Please enter PGP passphrase (or ENTER to abort):
I have no idea what PGP is, so only can enter to abort.

0. if we dont have local repository, do I still need ./sbt _publish-signed and spPublish?
1. it is mandatory to have ./sbt +publish-signed and ./sbt +spPublish to run? I dont have other project need this packages. however, if it ismandatory, please let me know how to get this PGP
2. I am more worry about build.sbt file, I can find example of this file in the URL, can you let me know where I can refer to?
3. After I have build.sbt file, I guess I can go on to RDD to dataFrame, since I have downloaded this drive. right?