Support Eshell iterative evaluation in the background

This really just generalizes Eshell's previous support for iterative
evaluation of a single current command to a list of multiple commands,
of which at most one can be in the foreground (bug#66066).

* lisp/eshell/esh-cmd.el (eshell-last-async-procs)
(eshell-current-command): Make obsolete in favor of...
(eshell-foreground-command): ... this
(eshell-background-commands): New variable.
(eshell-interactive-process-p): Make obsolete.
(eshell-head-process, eshell-tail-process): Use
'eshell-foreground-command'.
(eshell-cmd-initialize): Initialize new variables.
(eshell-add-command, eshell-remove-command)
(eshell-commands-for-process): New functions.
(eshell-parse-command): Make 'eshell-do-subjob' the outermost call.
(eshell-do-subjob): Call 'eshell-resume-eval' to split this command
off from its parent forms.
(eshell-eval-command): Use 'eshell-add-command'.
(eshell-resume-command): Use 'eshell-commands-for-process'.
(eshell-resume-eval): Take a COMMAND argument.  Return
':eshell-background' form for deferred background commands.
(eshell-do-eval): Remove check for 'eshell-current-subjob-p'.  This is
handled differently now.

* lisp/eshell/eshell.el (eshell-command): Wait for all processes to
exit when running synchronously.

* lisp/eshell/esh-mode.el (eshell-intercept-commands)
(eshell-watch-for-password-prompt):
* lisp/eshell/em-cmpl.el (eshell-complete-parse-arguments):
* lisp/eshell/em-smart.el (eshell-smart-display-move): Use
'eshell-foreground-command'.

* test/lisp/eshell/esh-cmd-tests.el
(esh-cmd-test/background/simple-command)
(esh-cmd-test/background/subcommand): New tests.
(esh-cmd-test/throw): Use 'eshell-foreground-command'.

* test/lisp/eshell/eshell-tests.el (eshell-test/queue-input): Use
'eshell-foreground-command'.

* test/lisp/eshell/em-script-tests.el
(em-script-test/source-script/background): Make the test script more
complex.

* test/lisp/eshell/eshell-tests.el
(eshell-test/eshell-command/pipeline-wait): New test.

* doc/misc/eshell.texi (Bugs and ideas): Remove implemented feature.

1 files changed, 2 insertions, 3 deletions

diff --git a/lisp/eshell/eshell.el b/lisp/eshell/eshell.el
index a3f80f453eb..8765ba499a1 100644
--- a/lisp/eshell/eshell.el
+++ b/lisp/eshell/eshell.el
@@ -315,9 +315,8 @@ argument), then insert output into the current buffer at point."
         ;; make the output as attractive as possible, with no
         ;; extraneous newlines
         (when intr
-          (if (eshell-interactive-process-p)
-              (eshell-wait-for-process (eshell-tail-process)))
-          (cl-assert (not (eshell-interactive-process-p)))
+          (apply #'eshell-wait-for-process (cadr eshell-foreground-command))
+          (cl-assert (not eshell-foreground-command))
           (goto-char (point-max))
           (while (and (bolp) (not (bobp)))
             (delete-char -1)))