bug#4343: comint-carriage-motion for async-shell-command

[Juri Linkov <juri@jurta.org>]

Often an asynchronous shell command run with M-& produces the output
that looks like garbage when programs use carriage control characters ^M
to display progress with percentages.

Even the `compile' command is better in this regard because its
`compilation-filter' handles carriage motion using the function
`comint-carriage-motion'.

The following patch does the same for asynchronous commands in
`shell-command'.  It seems it was intended to do this anyway because
`*Async Shell Command*' uses `shell-mode'.  But `shell-mode' doesn't set
the filter that processes carriage control characters.  It is the `shell'
command that sets the filter via `comint-exec' before enabling `shell-mode'.
So it's necessary to set the filter explicitly in `shell-command'
after enabling `shell-mode':

Index: lisp/simple.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/simple.el,v
retrieving revision 1.1008
diff -u -r1.1008 simple.el
--- lisp/simple.el	28 Aug 2009 04:21:17 -0000	1.1008
+++ lisp/simple.el	4 Sep 2009 21:02:21 -0000
@@ -2214,7 +2220,11 @@
 		  (setq mode-line-process '(":%s"))
 		  (require 'shell) (shell-mode)
 		  (set-process-sentinel proc 'shell-command-sentinel)
+		  ;; Use the comint filter for proper handling of carriage motion
+		  ;; (see `comint-inhibit-carriage-motion'),.
+		  (set-process-filter proc 'comint-output-filter)
 		  ))
 	    (shell-command-on-region (point) (point) command
 				     output-buffer nil error-buffer)))))))

-- 
Juri Linkov
http://www.jurta.org/emacs/