Improve docs for manually releasing (#228)

Author: raboof

RELEASING.md

@@ -14,7 +14,5 @@ It is often the case when this compiler plugin needs to be released for a newly
 1. Checkout the version that is to be back-released, which would be
   * master, if no features or bug fixes were merged to master since the latest release
   * tag, if the master has unreleased features or bug fixes. In this case you will need to cherry pick the commit that adds support for the new Scala version.
-2. Create a file `version.sbt` containing `version in ThisBuild := "0.11"` which sets the version to be back-released. This will override the automatic version derivation from the git history. Alternatively you can `set version in ThisBuild := ...` in the command line.
-3. Change the Scala version to the release you want to perform, this is done by `++2.12.11` in the sbt command line.
-4. Publish the release by running `sbt publishSigned`. You will need Sonatype OSS repository rights to publish under `com.typesafe` organisation.
-5. Login to [Sonatype](https://oss.sonatype.org/) to close and release the repository.
+1. Create a file `version.sbt` containing `version in ThisBuild := "0.11"` which sets the version to be back-released. This will override the automatic version derivation from the git history. Alternatively you can `set version in ThisBuild := ...` in the command line.
+1. Publish the release by running `SONATYPE_USERNAME=xxx SONATYPE_PASSWORD=xxx sbt ++2.12.11 publishSigned sonatypeBundleRelease` (with the appropriate credentials and scala version). You will need Sonatype OSS repository rights to publish under `com.typesafe` organisation.