Make sbt-release work with sbt-git versioning.

release.sbt

import sbtrelease._
import ReleaseKeys._
import Utilities._
import ReleaseStateTransformations._

val gitVersionString = """enablePlugins(GitVersioning)

git.baseVersion := "%s""""

def writeVersion(st: State, versionString: String) {
  val file = st.extract.get(releaseVersionFile)
  IO.write(file, versionString)
}

val globalVersionString = "version in ThisBuild := \"%s\""
val versionString = "version := \"%s\""

def setVersion(selectVersion: Versions => String, release: Boolean): ReleaseStep = { st: State =>

  val vs = st.get(versions)
    .getOrElse(sys.error("No versions are set! Was this release part executed before inquireVersions?"))
  val selected = selectVersion(vs)

  val useGlobal = st.extract.get(releaseUseGlobalVersion)

  st.log.info("Setting version to '%s'." format selected)

  val versionStr =
    if (release) {
      (if (useGlobal) globalVersionString else versionString) format selected
    }
    else {
      gitVersionString format Version(selected).map(_.withoutQualifier.string).getOrElse(versionFormatError)
    }

  writeVersion(st, versionStr)

  reapply(Seq(
    if (useGlobal) version in ThisBuild := selected
    else version := selected,
    git.baseVersion := Version(selected).map(_.withoutQualifier.string).getOrElse(versionFormatError)
  ), st)
}

lazy val setGitReleaseVersion: ReleaseStep = setVersion(_._1, true)
lazy val setGitNextVersion: ReleaseStep = setVersion(_._2, false)

releaseProcess := Seq[ReleaseStep](
  checkSnapshotDependencies,              // : ReleaseStep
  inquireVersions,                        // : ReleaseStep
  runTest,                                // : ReleaseStep
  setGitReleaseVersion,                   // : ReleaseStep
  commitReleaseVersion,                   // : ReleaseStep, performs the initial git checks
  tagRelease,                             // : ReleaseStep
  publishArtifacts,                       // : ReleaseStep, checks whether `publishTo` is properly set up
  setGitNextVersion,                      // : ReleaseStep
  commitNextVersion,                      // : ReleaseStep
  pushChanges                             // : ReleaseStep, also checks that an upstream branch is properly configured
)