bug#6963: More usecases, patch attached

[Wolfgang Schnerring <wosc@wosc.de>]

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emacsclient is such a usefull tool. But that it does not signal error
situations via its exit status severely hinders its usage in shell
scripts or in integration with other programs.

For example, I was bit by this rather badly when I tried to use
emacsclient to start an ediff session, to use as a merge tool for the
Mercurial SCM.
I may have made a typo in configuring said ediff command or for
whatever other reason, Emacs returned an error. But Mercurial was
blissfully unaware of this, since emacsclient returns 0 no matter
what. End result: Mercurial committed a broken merge that I had to
spend at least two hours some days later to debug.

I've attached a patch that makes emacsclient exit with nonzero status
when it receives an error message from Emacs -- it already *prints*
"*ERROR*" in these cases, so I feel this makes a lot of sense.

Thanks,
Wolfgang

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=== modified file 'lib-src/emacsclient.c'
--- lib-src/emacsclient.c	2010-08-11 08:20:34 +0000
+++ lib-src/emacsclient.c	2010-09-29 05:57:38 +0000
@@ -1506,6 +1506,7 @@
   char *cwd, *str;
   char string[BUFSIZ+1];
   int null_socket_name, null_server_file, start_daemon_if_needed;
+  int exit_status = EXIT_SUCCESS;
 
   main_argv = argv;
   progname = argv[0];
@@ -1746,6 +1747,7 @@
             printf ("\n");
           fprintf (stderr, "*ERROR*: %s", str);
           needlf = str[0] == '\0' ? needlf : str[strlen (str) - 1] != '\n';
+          exit_status = EXIT_FAILURE;
         }
 #ifdef SIGSTOP
       else if (strprefix ("-suspend ", string))
@@ -1764,6 +1766,7 @@
             printf ("\n");
           printf ("*ERROR*: Unknown message: %s", string);
           needlf = string[0] == '\0' ? needlf : string[strlen (string) - 1] != '\n';
+          exit_status = EXIT_FAILURE;
         }
     }
 
@@ -1773,7 +1776,7 @@
   fsync (1);
 
   CLOSE_SOCKET (emacs_socket);
-  return EXIT_SUCCESS;
+  return exit_status;
 }
 
 #endif /* HAVE_SOCKETS && HAVE_INET_SOCKETS */


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