diff --git a/main/State.scala b/main/State.scala
index 5f7820b1c..32e0895bd 100644
--- a/main/State.scala
+++ b/main/State.scala
@@ -7,6 +7,18 @@ package sbt
 	import java.util.concurrent.Callable
 	import CommandSupport.{FailureWall, logger}
 
+/**
+Data structure representing all command execution information.
+
+@param `configuration` provides access to the launcher environment, including the application configuration, Scala versions, jvm/filesystem wide locking, and the launcher itself
+@param definedCommands the list of command definitions that evaluate command strings.  These may be modified to change the available commands.
+@param onFailure the command to execute when another command fails.  `onFailure` is cleared before the failure handling command is executed.
+@param remainingCommands the sequence of commands to execute.  This sequence may be modified to change the commands to be executed.  Typically, the `::` and `:::` methods are used to prepend new commands to run.
+@param exitHooks code to run before sbt exits, usually to ensure resources are cleaned up.
+@param history tracks the recently executed commands
+@param attributes custom command state.  It is important to clean up attributes when no longer needed to avoid memory leaks and class loader leaks.
+@param next the next action for the command processor to take.  This may be to continue with the next command, adjust global logging, or exit.
+*/
 final case class State(
 	configuration: xsbti.AppConfiguration,
 	definedCommands: Seq[Command],
@@ -26,53 +38,107 @@ trait Identity {
 	override final def toString = super.toString
 }
 
+/** Convenience methods for State transformations and operations. */
 trait StateOps {
 	def process(f: (String, State) => State): State
+
+	/** Schedules `commands` to be run before any remaining commands.*/
 	def ::: (commands: Seq[String]): State
+
+	/** Schedules `command` to be run before any remaining commands.*/
 	def :: (command: String): State
+
+	/** Sets the next command processing action to be to continue processing the next command.*/
 	def continue: State
+
+	/** Reboots sbt.  A reboot restarts execution from the entry point of the launcher.
+	* A reboot is designed to be as close as possible to actually restarting the JVM without actually doing so.
+	* Because the JVM is not restarted, JVM exit hooks are not run.
+	* State.exitHooks should be used instead and those will be run before rebooting.
+	* If `full` is true, the boot directory is deleted before starting again.
+	* This command is currently implemented to not return, but may be implemented in the future to only reboot at the next command processing step. */
 	def reboot(full: Boolean): State
+
+	/** Sets the next command processing action to do.*/
 	def setNext(n: State.Next): State
+
 	@deprecated("Use setNext", "0.11.0") def setResult(ro: Option[xsbti.MainResult])
+
+	/** Restarts sbt without dropping loaded Scala classes.  It is a shallower restart than `reboot`.*/
 	def reload: State
+
+	/** Sets the next command processing action to be to rotate the global log and continue executing commands.*/
 	def clearGlobalLog: State
+	/** Sets the next command processing action to be to keep the previous log and continue executing commands.  */
 	def keepLastLog: State
+
+	/** Sets the next command processing action to be to exit with a zero exit code if `ok` is true and a nonzero exit code if `ok` if false.*/
 	def exit(ok: Boolean): State
+	/** Marks the currently executing command as failing.  This triggers failure handling by the command processor.  See also `State.onFailure`*/
 	def fail: State
+
+	/** Schedules `newCommands` to be run after any remaining commands. */
 	def ++ (newCommands: Seq[Command]): State
+	/** Schedules `newCommand` to be run after any remaining commands. */
 	def + (newCommand: Command): State
+
+	/** Gets the value associated with `key` from the custom attributes map.*/
 	def get[T](key: AttributeKey[T]): Option[T]
+	/** Sets the value associated with `key` in the custom attributes map.*/
 	def put[T](key: AttributeKey[T], value: T): State
+	/** Removes the `key` and any associated value from the custom attributes map.*/
 	def remove(key: AttributeKey[_]): State
+	/** Sets the value associated with `key` in the custom attributes map by transforming the current value.*/
 	def update[T](key: AttributeKey[T])(f: Option[T] => T): State
+	/** Returns true if `key` exists in the custom attributes map, false if it does not exist.*/
 	def has(key: AttributeKey[_]): Boolean
+
+	/** The application base directory, which is not necessarily the current working directory.*/
 	def baseDir: File
+
+	/** The Logger used for general command logging.*/
 	def log: Logger
+
+	/** Evaluates the provided expression with a JVM-wide and machine-wide lock on `file`.*/
 	def locked[T](file: File)(t: => T): T
+
+	/** Runs any defined exitHooks and then clears them.*/
 	def runExitHooks(): State
+	/** Registers a new exit hook, which will run when sbt exits or restarts.*/
 	def addExitHook(f: => Unit): State
 }
+
 object State
 {
+	/** Represents the next action for the command processor.*/
 	sealed trait Next
+	/** Indicates that the command processor should process the next command.*/
 	object Continue extends Next
+	/** Indicates that the application should exit with the given result.*/
 	final class Return(val result: xsbti.MainResult) extends Next
+	/** Indicates that global logging should be rotated.*/
 	final object ClearGlobalLog extends Next
+	/** Indicates that the previous log file should be preserved instead of discarded.*/
 	final object KeepLastLog extends Next
 
-	/** Provides a list of recently executed commands.  The commands are stored as processed instead of as entered by the user.*/
+	/** Provides a list of recently executed commands.  The commands are stored as processed instead of as entered by the user.
+	* @param executed the list of the most recently executed commands, with the most recent command first.
+	* @maxSize the maximum number of commands to keep, or 0 to keep an unlimited number. */
 	final class History private[State](val executed: Seq[String], val maxSize: Int)
 	{
+		/** Adds `command` as the most recently executed command.*/
 		def :: (command: String): History =
 		{
-			val prependTo = if(executed.size >= maxSize) executed.take(maxSize - 1) else executed
+			val prependTo = if(maxSize > 0 && executed.size >= maxSize) executed.take(maxSize - 1) else executed
 			new History(command +: prependTo, maxSize)
 		}
+		/** Changes the maximum number of commands kept, adjusting the current history if necessary.*/
 		def setMaxSize(size: Int): History =
-			new History(executed.take(size), size)
+			new History(if(size <= 0) executed else executed.take(size), size)
 		def current: String = executed.head
 		def previous: Option[String] = executed.drop(1).headOption
 	}
+	/** Constructs an empty command History with a default, finite command limit.*/
 	def newHistory = new History(Vector.empty, complete.HistoryCommands.MaxLines)
 
 	def defaultReload(state: State): Reboot =
@@ -81,6 +147,7 @@ object State
 		new Reboot(app.scalaProvider.version, state.remainingCommands, app.id, state.configuration.baseDirectory)
 	}
 
+	/** Provides operations and transformations on State. */
 	implicit def stateOps(s: State): StateOps = new StateOps {
 		def process(f: (String, State) => State): State =
 			s.remainingCommands match {