sbt prompt with git branch and git status for modifications etc.

build.sbt

// the following results in 
// superduperproject : master : 0.1.0 : MD??>
// where M => Modified, D => Deleted, ?? => not tracked 
// and might include (not tested :))
// !, R, C, U  for details check https://www.kernel.org/pub/software/scm/git/docs/git-status.html#_short_format  
// if you see  superduperproject : master : 0.1.0 : -?->  ... well then oops and happy debugging and do tell... 

shellPrompt in ThisBuild := ShellPrompt.buildShellPrompt("0.1.0")

build.scala

// sbt 0.13+ 
// how often a prompt gets updated? can't tell 
// lifted from http://www.scala-sbt.org/release/docs/Examples/Full-Configuration-Example.html and modified 

object ShellPrompt {
  object devnull extends ProcessLogger {
    def info (s: => String) {}
    def error (s: => String) { }
    def buffer[T] (f: => T): T = f
  }

  val oops = "-?-"

  def currBranch = ("git branch" lines_! devnull headOption) getOrElse oops stripPrefix "* "

  def currModifications = ("git status -sb" lines_! devnull tail).foldLeft("")(
      (a,n) =>n.trim.split(" ").headOption.map(m => if(a.contains(m)) a else a + m) getOrElse oops
    ) // can do better?

  def buildShellPrompt(ver: String) = {
    (state: State) => {
      val currProject = Project.extract (state).currentProject.id
      "%s : %s : %s : %s> ".format (
        currProject, currBranch, ver, currModifications
      )
    }
  }
}