diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 08823ddd8..6f6d87650 100755
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -1349,6 +1349,7 @@ object Classpaths
 
 	lazy val typesafeReleases = Resolver.typesafeIvyRepo("releases")
 	lazy val typesafeSnapshots = Resolver.typesafeIvyRepo("snapshots")
+
 	@deprecated("Use `typesafeReleases` instead", "0.12.0")
 	lazy val typesafeResolver = typesafeReleases
 	@deprecated("Use `Resolver.typesafeIvyRepo` instead", "0.12.0")
@@ -1422,7 +1423,7 @@ object Classpaths
 	@deprecated("Directly provide the jar files per Scala version.", "0.13.0")
 	def substituteScalaFiles(scalaInstance: ScalaInstance, scalaOrg: String, report: UpdateReport): UpdateReport =
 		substituteScalaFiles(scalaOrg, report)(const(scalaInstance.jars))
-		
+
 	def substituteScalaFiles(scalaOrg: String, report: UpdateReport)(scalaJars: String => Seq[File]): UpdateReport =
 		report.substitute { (configuration, module, arts) =>
 			if(module.organization == scalaOrg) {
@@ -1496,24 +1497,37 @@ trait BuildExtra extends BuildCommon
 		def compose(setting: SettingKey[State => State], f: State => State) = setting in Global ~= (_ compose f)
 		Seq( compose(onLoad, add), compose(onUnload, remove) )
 	}
+
+	/** Adds `dependency` as an sbt plugin for the specific sbt version `sbtVersion` and Scala version `scalaVersion`.
+	* Typically, use the default values for these versions instead of specifying them explicitly. */
 	def addSbtPlugin(dependency: ModuleID, sbtVersion: String, scalaVersion: String): Setting[Seq[ModuleID]] =
 		libraryDependencies += sbtPluginExtra(dependency, sbtVersion, scalaVersion)
+
+	/** Adds `dependency` as an sbt plugin for the specific sbt version `sbtVersion`.
+	* Typically, use the default value for this version instead of specifying it explicitly. */
 	def addSbtPlugin(dependency: ModuleID, sbtVersion: String): Setting[Seq[ModuleID]] =
 		libraryDependencies <+= (scalaBinaryVersion in update) { scalaV => sbtPluginExtra(dependency, sbtVersion, scalaV) }
+
+	/** Adds `dependency` as an sbt plugin for the sbt and Scala versions configured by
+	* `sbtBinaryVersion` and `scalaBinaryVersion` scoped to `update`. */
 	def addSbtPlugin(dependency: ModuleID): Setting[Seq[ModuleID]] =
 		libraryDependencies <+= (sbtBinaryVersion in update,scalaBinaryVersion in update) { (sbtV, scalaV) => sbtPluginExtra(dependency, sbtV, scalaV) }
 
+	/** Transforms `dependency` to be in the auto-compiler plugin configuration. */
 	def compilerPlugin(dependency: ModuleID): ModuleID =
 		dependency.copy(configurations = Some("plugin->default(compile)"))
 
+	/** Adds `dependency` to `libraryDependencies` in the auto-compiler plugin configuration. */
 	def addCompilerPlugin(dependency: ModuleID): Setting[Seq[ModuleID]] =
 		libraryDependencies += compilerPlugin(dependency)
 
+	/** Constructs a setting that declares a new artifact `a` that is generated by `taskDef`. */
 	def addArtifact(a: Artifact, taskDef: TaskKey[File]): SettingsDefinition =
 	{
 		val pkgd = packagedArtifacts := packagedArtifacts.value updated (a, taskDef.value)
 		seq( artifacts += a, pkgd )
 	}
+	/** Constructs a setting that declares a new artifact `artifact` that is generated by `taskDef`. */
 	def addArtifact(artifact: Initialize[Artifact], taskDef: Initialize[Task[File]]): SettingsDefinition =
 	{
 		val artLocal = SettingKey.local[Artifact]
@@ -1588,20 +1602,27 @@ trait BuildCommon
 	def inputTask[T](f: TaskKey[Seq[String]] => Initialize[Task[T]]): Initialize[InputTask[T]] =
 		InputTask.apply(Def.value((s: State) => Def.spaceDelimited()))(f)
 
+	/** Allows a String to be used where a `NameFilter` is expected.
+	* Asterisks (`*`) in the string are interpreted as wildcards.
+	* All other characters must match exactly.  See [[sbt.GlobFilter]]. */
 	implicit def globFilter(expression: String): NameFilter = GlobFilter(expression)
+
 	implicit def richAttributed(s: Seq[Attributed[File]]): RichAttributed = new RichAttributed(s)
 	implicit def richFiles(s: Seq[File]): RichFiles = new RichFiles(s)
 	implicit def richPathFinder(s: PathFinder): RichPathFinder = new RichPathFinder(s)
 	final class RichPathFinder private[sbt](s: PathFinder)
 	{
+		/** Converts the `PathFinder` to a `Classpath`, which is an alias for `Seq[Attributed[File]]`. */
 		def classpath: Classpath = Attributed blankSeq s.get
 	}
 	final class RichAttributed private[sbt](s: Seq[Attributed[File]])
 	{
+		/** Extracts the plain `Seq[File]` from a Classpath (which is a `Seq[Attributed[File]]`).*/
 		def files: Seq[File] = Attributed.data(s)
 	}
 	final class RichFiles private[sbt](s: Seq[File])
 	{
+		/** Converts the `Seq[File]` to a Classpath, which is an alias for `Seq[Attributed[File]]`. */
 		def classpath: Classpath = Attributed blankSeq s
 	}
 	def toError(o: Option[String]): Unit = o foreach error