from http://www.scala-sbt.org/release/docs/Using-Sonatype.html
The credentials for your Sonatype OSSRH account need to be stored somewhere safe (e.g. NOT in the repository). Common convention is a ~/.sbt/1.0/sonatype.sbt file with the following:
credentials += Credentials("Sonatype Nexus Repository Manager",
"oss.sonatype.org",
"<your username>",
"<your password>")
To release and publish a version to oss.sonatype for both scala 2.11 and scala 2.12 run:
sbt release
To only publish a certain version after f.e. the tags has been build but your PGP was not correctly unlocked you can run
sbt ++2.11.12 publishSigned
To close and release the staging repository on Sonatype you can either go to the web interface or use
sbt sonatypeRelease