Show when bazel run exited with code

[KoltesDigital]

Hi,

As I'm using ibazel to develop and run a short-lived binary, I though it'd be good to have ibazel show when the binary has exited. A message "Starting..." is displayed at the beginning, this PR adds a message "Exited (code)" at the end.

I'm a bit frustrated that the OS can't tell exactly which child has exited, but AFAIK when there's a Command no other Cmd is spawned.

I have no idea how to write tests for that... and I hope it won't catch grandchildren.

[KoltesDigital]

Well, the CI has shown the tests, and that there's no SIGCHLD on Windows. I guess the next solution is to spawn a thread that waits on the Cmd, and that would revert the signal handling.

[KoltesDigital]

Ok now a goroutine is responsible for waiting, so it can't be done elsewhere: command structs gain two sync vars to report back, one atomic bool for whether it's running, and a channel to deal with the terminate timeout.

Bazel struct loses its Wait as it wasn't called anywhere, and I believe it's not exported into a library.

[achew22]

Looks like a good start. Could you add some end to end tests to cover this new behavior so we don't accidentally regress it?

[KoltesDigital]

@achew22 You're right, here's the e2e test.

However there's a data race I cannot get rid of. My guess it that the waiting goroutine from another test is still running when a new test starts. I've tried to ensure that the goroutine won't cross test boundaries (eg. calling cmd.Terminate() in IBazel.Cleanup, given that terminate should wait for it in any case) with no success. Do you have an idea about that?