add LICENSE.txt to all packaged jars.

update license year

(cherry picked from commit b23c54a)

LICENSE.txt

@@ -1,4 +1,4 @@
-Copyright (c) 2009-2014 Tony Morris, Runar Bjarnason, Tom Adams, Kristian Domagala, Brad Clow, Ricky Clarkson, Paul Chiusano, Trygve Laugstøl, Nick Partridge, Jason Zaugg, Sam Halliday
+Copyright (c) 2009-2018 Tony Morris, Runar Bjarnason, Tom Adams, Kristian Domagala, Brad Clow, Ricky Clarkson, Paul Chiusano, Trygve Laugstøl, Nick Partridge, Jason Zaugg, Sam Halliday
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without

project/build.scala

@@ -275,11 +275,20 @@ object build {
         }
         </developers>
       ),
+
+    licenseFile := {
+      val LICENSE_txt = (baseDirectory in ThisBuild).value / "LICENSE.txt"
+      if (!LICENSE_txt.exists()) sys.error(s"cannot find license file at $LICENSE_txt")
+      LICENSE_txt
+    },
     // kind-projector plugin
     resolvers += Resolver.sonatypeRepo("releases"),
     kindProjectorVersion := "0.9.7",
     libraryDependencies += compilerPlugin("org.spire-math" % "kind-projector" % kindProjectorVersion.value cross CrossVersion.binary)
-  ) ++ SbtOsgi.projectSettings ++ Seq[Sett](
+  ) ++ Seq(packageBin, packageDoc, packageSrc).flatMap {
+    // include LICENSE.txt in all packaged artifacts
+    inTask(_)(Seq(mappings in Compile += licenseFile.value -> "LICENSE"))
+  } ++ SbtOsgi.projectSettings ++ Seq[Sett](
     OsgiKeys.additionalHeaders := Map("-removeheaders" -> "Include-Resource,Private-Package")
   )
 
@@ -379,6 +388,8 @@ object build {
     }
   }
 
+  lazy val licenseFile = settingKey[File]("The license file to include in packaged artifacts")
+
   lazy val genTypeClasses = taskKey[Seq[(FileStatus, File)]]("")
 
   lazy val typeClasses = taskKey[Seq[TypeClass]]("")