updated for version 7.4.414

Problem:    Cannot define a command only when it's used.
Solution:   Add the CmdUndefined autocommand event. (partly by Yasuhiro
            Matsumoto)

runtime/doc/autocmd.txt

@@ -278,6 +278,7 @@ Name			triggered by ~
 |ShellCmdPost|		after executing a shell command
 |ShellFilterPost|	after filtering with a shell command
 
+|CmdUndefined|		a user command is used but it isn't defined
 |FuncUndefined|		a user function is used but it isn't defined
 |SpellFileMissing|	a spell file is used but it can't be found
 |SourcePre|		before sourcing a Vim script
@@ -465,6 +466,16 @@ BufWriteCmd			Before writing the whole buffer to a file.
 							*BufWritePost*
 BufWritePost			After writing the whole buffer to a file
 				(should undo the commands for BufWritePre).
+							*CmdUndefined*
+CmdUndefined			When a user command is used but it isn't
+				defined.  Useful for defining a command only
+				when it's used.  The pattern is matched
+				against the command name.  Both <amatch> and
+				<afile> are set to the name of the command.
+				NOTE: Autocompletion won't work until the
+				command is defined.  An alternative is to
+				always define the user command and have it
+				invoke an autoloaded function.  See |autoload|.
 							*CmdwinEnter*
 CmdwinEnter			After entering the command-line window.
 				Useful for setting options specifically for
@@ -670,6 +681,8 @@ FuncUndefined			When a user function is used but it isn't
 				when it's used.  The pattern is matched
 				against the function name.  Both <amatch> and
 				<afile> are set to the name of the function.
+				NOTE: When writing Vim scripts a better
+				alternative is to use an autoloaded function.
 				See |autoload-functions|.
 							*GUIEnter*
 GUIEnter			After starting the GUI successfully, and after

src/ex_docmd.c

@@ -2143,6 +2143,26 @@ do_one_cmd(cmdlinep, sourcing,
     /* Find the command and let "p" point to after it. */
     p = find_command(&ea, NULL);
 
+#ifdef FEAT_AUTOCMD
+    /* If this looks like an undefined user command and there are CmdUndefined
+     * autocommands defined, trigger the matching autocommands. */
+    if (p != NULL && ea.cmdidx == CMD_SIZE && !ea.skip
+	    && ASCII_ISUPPER(*ea.cmd)
+	    && has_cmdundefined())
+    {
+	char_u *p = ea.cmd;
+	int ret;
+
+	while (ASCII_ISALNUM(*p))
+	    ++p;
+	p = vim_strnsave(ea.cmd, p - ea.cmd);
+	ret = apply_autocmds(EVENT_CMDUNDEFINED, p, p, TRUE, NULL);
+	vim_free(p);
+	if (ret && !aborting())
+	    p = find_command(&ea, NULL);
+    }
+#endif
+
 #ifdef FEAT_USR_CMDS
     if (p == NULL)
     {

src/fileio.c

@@ -7641,6 +7641,7 @@ static struct event_name
     {"BufWriteCmd",	EVENT_BUFWRITECMD},
     {"CmdwinEnter",	EVENT_CMDWINENTER},
     {"CmdwinLeave",	EVENT_CMDWINLEAVE},
+    {"CmdUndefined",	EVENT_CMDUNDEFINED},
     {"ColorScheme",	EVENT_COLORSCHEME},
     {"CompleteDone",	EVENT_COMPLETEDONE},
     {"CursorHold",	EVENT_CURSORHOLD},
@@ -9159,6 +9160,24 @@ has_insertcharpre()
     return (first_autopat[(int)EVENT_INSERTCHARPRE] != NULL);
 }
 
+/*
+ * Return TRUE when there is an CmdUndefined autocommand defined.
+ */
+    int
+has_cmdundefined()
+{
+    return (first_autopat[(int)EVENT_CMDUNDEFINED] != NULL);
+}
+
+/*
+ * Return TRUE when there is an FuncUndefined autocommand defined.
+ */
+    int
+has_funcundefined()
+{
+    return (first_autopat[(int)EVENT_FUNCUNDEFINED] != NULL);
+}
+
     static int
 apply_autocmds_group(event, fname, fname_io, force, group, buf, eap)
     event_T	event;

src/proto/fileio.pro

@@ -47,6 +47,8 @@ int has_cursormovedI __ARGS((void));
 int has_textchanged __ARGS((void));
 int has_textchangedI __ARGS((void));
 int has_insertcharpre __ARGS((void));
+int has_cmdundefined __ARGS((void));
+int has_funcundefined __ARGS((void));
 void block_autocmds __ARGS((void));
 void unblock_autocmds __ARGS((void));
 int is_autocmd_blocked __ARGS((void));

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    414,
 /**/
     413,
 /**/