Add support for arguments in ALTERNATE_EDITOR to emacsclient

* lib-src/emacsclient.c (fail): Parse ALTERNATE_EDITOR, or
corresponding command-line argument, into space-separated tokens.
* etc/NEWS: Document.
* test/lib-src/emacsclient-tests.el: Add a test.

etc/NEWS

@@ -505,6 +505,10 @@ Linum mode and all similar packages are henceforth becoming obsolete.
 Users and developers are encouraged to switch to this new feature
 instead.
 
++++
+** emacsclient now accepts command-line options in ALTERNATE_EDITOR
+and --alternate-editor. For example, ALTERNATE_EDITOR="emacs -Q -nw".
+
 
 * Editing Changes in Emacs 26.1
 

lib-src/emacsclient.c

@@ -110,6 +110,9 @@ char *w32_getenv (const char *);
 /* Name used to invoke this program.  */
 const char *progname;
 
+/* The first argument to main.  */
+int main_argc;
+
 /* The second argument to main.  */
 char **main_argv;
 
@@ -201,6 +204,35 @@ xmalloc (size_t size)
   return result;
 }
 
+/* Like realloc but get fatal error if memory is exhausted.  */
+
+static void *
+xrealloc (void *ptr, size_t size)
+{
+  void *result = realloc (ptr, size);
+  if (result == NULL)
+    {
+      perror ("realloc");
+      exit (EXIT_FAILURE);
+    }
+  return result;
+}
+
+/* Like strdup but get a fatal error if memory is exhausted. */
+char *xstrdup (const char *);
+
+char *
+xstrdup (const char *s)
+{
+  char *result = strdup (s);
+  if (result == NULL)
+    {
+      perror ("strdup");
+      exit (EXIT_FAILURE);
+    }
+  return result;
+}
+
 /* From sysdep.c */
 #if !defined (HAVE_GET_CURRENT_DIR_NAME) || defined (BROKEN_GET_CURRENT_DIR_NAME)
 
@@ -264,21 +296,6 @@ get_current_dir_name (void)
 
 #ifdef WINDOWSNT
 
-/* Like strdup but get a fatal error if memory is exhausted. */
-char *xstrdup (const char *);
-
-char *
-xstrdup (const char *s)
-{
-  char *result = strdup (s);
-  if (result == NULL)
-    {
-      perror ("strdup");
-      exit (EXIT_FAILURE);
-    }
-  return result;
-}
-
 #define REG_ROOT "SOFTWARE\\GNU\\Emacs"
 
 char *w32_get_resource (HKEY, const char *, LPDWORD);
@@ -673,7 +690,7 @@ Report bugs with M-x report-emacs-bug.\n");
 }
 
 /* Try to run a different command, or --if no alternate editor is
-   defined-- exit with an errorcode.
+   defined-- exit with an decoderde.
    Uses argv, but gets it from the global variable main_argv.  */
 
 static _Noreturn void
@@ -681,9 +698,27 @@ fail (void)
 {
   if (alternate_editor)
     {
-      int i = optind - 1;
+      size_t extra_args_size = (main_argc - optind + 1) * sizeof (char *);
+      size_t new_argv_size = extra_args_size;
+      char **new_argv = NULL;
+      /* Needed because strtok overwrites its input.  */
+      char *s = xstrdup (alternate_editor);
+      unsigned toks = 0;
+      char *tok = strtok(s, " ");
 
-      execvp (alternate_editor, main_argv + i);
+      /* Unpack alternate_editor's space-separated tokens into new_argv.  */
+      do
+        {
+          toks++;
+          new_argv = xrealloc (new_argv, new_argv_size + toks * sizeof (char *));
+          new_argv[toks - 1] = tok;
+        }
+      while ((tok = strtok (NULL, " ")));
+
+      /* Append main_argv arguments to new_argv.  */
+      memcpy (&new_argv[toks], main_argv + optind, extra_args_size);
+
+      execvp (s, new_argv);
       message (true, "%s: error executing alternate editor \"%s\"\n",
 	       progname, alternate_editor);
     }
@@ -696,6 +731,7 @@ fail (void)
 int
 main (int argc, char **argv)
 {
+  main_argc = argc;
   main_argv = argv;
   progname = argv[0];
   message (true, "%s: Sorry, the Emacs server is supported only\n"
@@ -1629,6 +1665,7 @@ main (int argc, char **argv)
   int start_daemon_if_needed;
   int exit_status = EXIT_SUCCESS;
 
+  main_argc = argc;
   main_argv = argv;
   progname = argv[0];
 

test/lib-src/emacsclient-tests.el

@@ -0,0 +1,33 @@
+;;; process-tests.el --- Test emacsclient
+
+;; Copyright (C) 2016 Free Software Foundation, Inc.
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;
+
+;;; Code:
+
+(require 'ert)
+
+(ert-deftest emacsclient-test-alternate-editor-allows-arguments ()
+  (setenv "ALTERNATE_EDITOR" "emacs --batch")
+  (should
+   (= 0
+      (call-process "emacsclient" nil nil nil "foo"))))
+
+(provide 'emacsclient-tests)
+;; emacsclient-tests.el ends here.