Previously, we only waited until the tail process was finished, but
now, we wait for all of them. This is more consistent with other
shells, and prevents some cases of a process's output coming *after*
we continued past its pipeline.
* lisp/eshell/esh-cmd.el (eshell-resume-command): Simplify
conditionals, and check that all the foreground processes are dead
before resuming Eshell command.
* test/lisp/eshell/esh-cmd-tests.el
(esh-cmd-test/pipeline-wait/multi-proc): New test.
2ec41c174f