$ copy-file changes/B.scala B.scala

$ copy-file changes/A1.scala a/A.scala
> run 1
$ copy-file changes/A2.scala a/A.scala

# done this way because last modified times often have ~1s resolution
$ sleep 2000
> run 2
$ copy-file changes/A3.scala a/A.scala

$ sleep 2000
> run 3

$ copy-file changes/build2.sbt build.sbt
> reload

$ copy-file changes/A1.scala a/A.scala
> run 1
$ copy-file changes/A2.scala a/A.scala

$ sleep 2000
> run 2
$ copy-file changes/A3.scala a/A.scala

$ sleep 2000
> run 3