Build.scala for merging reference.conf

Build.scala

import sbt._
import Keys._
import classpath.ClasspathUtilities.isArchive
import java.io.FileOutputStream
import sbtassembly.Plugin._
import AssemblyKeys._

object B extends Build {
 lazy val merge = TaskKey[File]("merge-reference",
                       "merge all reference.conf")

 lazy val mergeSettings: Seq[Project.Setting[_]] = Seq(
  merge <<= (fullClasspath in assembly) map { c =>
    // collect from all elements of the full classpath
    val (libs, dirs) =
      c map (_.data) partition (isArchive)
    // goal is to simply concatenate files here
    val dest = file("reference.conf")
    val out = new FileOutputStream(dest)
    val append = IO.transfer(_: File, out)
    try {
     // first collect from managed sources
     (dirs * "reference.conf").get foreach append
     // then from dependency jars by unzipping and
     // collecting reference.conf if present
     for (lib <- libs) {
      IO withTemporaryDirectory { dir =>
       IO.unzip(lib, dir, "reference.conf")
       (dir * "reference.conf").get foreach append
      }
     }
     // return merged file location as task result
     dest
    } finally {
     out.close()
    }
   },

  // get rid of the individual files from jars
  excludedFiles in assembly <<=
    (excludedFiles in assembly) {
      (old) => (bases) =>
        old(bases) ++ (bases flatMap (base =>
          (base / "reference.conf").get))
    },

  // tell sbt-assembly to include our merged file
  assembledMappings in assembly <<=
    (assembledMappings in assembly, merge) map {
      (old, merged) => (f) =>
        old(f) :+ (merged, "reference.conf")
    }
 )

 lazy val project = Project("fail", file("."),
   settings = Defaults.defaultSettings ++
              assemblySettings ++ mergeSettings)
}

plugins.sbt

resolvers += Resolver.url("sbt-plugin-releases",
  new URL("http://scalasbt.artifactoryonline.com/scalasbt/sbt-plugin-releases/"))(Resolver.ivyStylePatterns)

addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.7.4")