SI-6419 Repl save session command

A simple save command to write out the current replay stack.

```
scala> val i = 7
i: Int = 7

scala> val j=  8
j: Int = 8

scala> i * j
res0: Int = 56

scala> :save multy.script

scala> :q
apm@mara:~/tmp$ cat multy.script
val i = 7
val j=  8
i * j
apm@mara:~/tmp$ skala
Welcome to Scala version 2.11.0-20130626-204845-a83ca5bdf7 (OpenJDK 64-Bit Server VM, Java 1.7.0_21).
Type in expressions to have them evaluated.
Type :help for more information.

scala> :load multy.script
Loading multy.script...
i: Int = 7
j: Int = 8
res0: Int = 56

scala> :load multy.script
Loading multy.script...
i: Int = 7
j: Int = 8
res1: Int = 56
```

1 files changed, 7 insertions, 0 deletions

diff --git a/src/repl/scala/tools/nsc/interpreter/ILoop.scala b/src/repl/scala/tools/nsc/interpreter/ILoop.scala
index a84d076e76..392aac7c2e 100644
--- a/src/repl/scala/tools/nsc/interpreter/ILoop.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ILoop.scala
@@ -220,6 +220,7 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
     nullary("quit", "exit the interpreter", () => Result(keepRunning = false, None)),
     nullary("replay", "reset execution and replay all previous commands", replay),
     nullary("reset", "reset the repl to its initial state, forgetting all session entries", resetCommand),
+    cmd("save", "<path>", "save replayable session to a file", saveCommand),
     shCommand,
     nullary("silent", "disable/enable automatic printing of results", verbosity),
     cmd("type", "[-v] <expr>", "display the type of an expression without evaluating it", typeCommand),
@@ -470,6 +471,12 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
     Result(keepRunning = true, shouldReplay)
   }
 
+  def saveCommand(filename: String): Result = (
+    if (filename.isEmpty) echo("File name is required.")
+    else if (replayCommandStack.isEmpty) echo("No replay commands in session")
+    else File(filename).printlnAll(replayCommands: _*)
+  )
+
   def addClasspath(arg: String): Unit = {
     val f = File(arg).normalize
     if (f.exists) {