alternative to `set every` in SBT

append.log

% sbt 'appendScalacOptions -Ydebug' "show scalacOptions" "show test:scalacOptions"
[info] Loading global plugins from /Users/jason/.sbt/0.13/plugins
[info] Loading project definition from /Users/jason/code/scratch3/project
[info] Set current project to scratch3 (in build file:/Users/jason/code/scratch3/)
[info] Reapplying settings...
[info] Set current project to scratch3 (in build file:/Users/jason/code/scratch3/)
[info] b/*:scalacOptions
[info] 	List(-Ydebug)
[info] a/*:scalacOptions
[info] 	List(-Xcheckinit, -Ydebug)
[info] scratch3/compile:scalacOptions
[info] 	List(-Ydebug)
[success] Total time: 0 s, completed May 12, 2014 11:21:47 AM
[info] Updating {file:/Users/jason/code/scratch3/}b...
[info] Updating {file:/Users/jason/code/scratch3/}a...
[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] Done updating.
[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] Done updating.
[info] b/test:scalacOptions
[info] 	List(-Ydebug)
[info] a/test:scalacOptions
[info] 	List(-Xcheckinit, -Xprint:typer, -Ydebug)
[info] scratch3/test:scalacOptions
[info] 	List(-Ydebug)

build.sbt

val a = project.settings(scalacOptions := Seq("-Xcheckinit"), scalacOptions in Test += "-Xprint:typer")

val b = project.settings(scalacOptions += "-Ydebug")

def appendScalacOptions(s: State, args: Seq[String]): State = {
  val extracted = Project extract s
  def appendDistinct[A](x: Seq[A], y: Seq[A]) = x.filterNot(y.contains) ++ y
  import extracted._
  val r = Project.relation(extracted.structure, true)
  val allDefs = r._1s.toSeq
  val projectScope = Load.projectScope(currentRef)
  val scopes = allDefs.filter(_.key == scalacOptions.key).map(_.scope).distinct
  val redefined = scopes.map(scope => scalacOptions in scope := appendDistinct((scalacOptions in scope).value, args))
  val session = extracted.session.appendRaw(redefined)
  BuiltinCommands.reapply(session, structure, s)  
}

commands += Command.args("appendScalacOptions", "<option>")(appendScalacOptions)

set-every.log

sbt 'set every scalacOptions in Compile += "-Ydebug"'
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=384m; support was removed in 8.0
[info] Loading global plugins from /Users/jason/.sbt/0.13/plugins
[info] Loading project definition from /Users/jason/code/scratch3/project
[info] Set current project to scratch3 (in build file:/Users/jason/code/scratch3/)
[info] Defining */*:scalacOptions, a/*:scalacOptions and 6 others.
[info] The new values will be used by a/compile:compile::compileInputs, a/compile:console and 28 others.
[info] 	Run `last` for details.
[info] Reapplying settings...
Cyclic reference involving
   {file:/Users/jason/code/scratch3/}scratch3/compile:scalacOptions
   */*:scalacOptions
	at sbt.Dag$Cyclic.$colon$colon(Dag.scala:68)

	at xsbt.boot.Boot.main(Boot.scala)
[error] Cyclic reference involving
[error]    {file:/Users/jason/code/scratch3/}scratch3/compile:scalacOptions
[error]    */*:scalacOptions
[error] Use 'last' for the full log.

It looks like projectScope is not used above.