Refactoring exec_process
The exec_process function is so complex. It should be refactored.
As a side effect of this refactoring, I think a bug can be fixed where redirections for a subshell command are not evaluated in the current shell.
unset x (:) < ${x=/dev/null} echo $x
Done in r4130, r4132, r4133, r4134, r4135
The exec_process function is so complex. It should be refactored.