Mill in interactive mode does not forward stdin/stdout correctly.

[megri]

Tested with Mill version: 0.12.5

I think there may be an issue with mill's stdin/-out forwarding. Running this:

def main(args: Array[String]): Unit =
    Iterator.from(0).takeWhile(_ => !Console.out.checkError()).foreach(println)

with mill -i thing.run | head -100 prints the first 100 elements and then keeps the process running.

If I first build a jar with mill thing.assembly and run java -jar out/thing/assembly.dest/out.jar | head -100 it works as expected, printing 100 items and then existing.

[lihaoyi]

Should be fixed in recent versions by #6220, which marked run with exclusive = true so it forwards the raw streams to the subprocess and bypasses Mill's logging infrastructure that did not handle checkError correctly