(command_loop_1): Handle values `only' and `identity' for Vtransient_mark_mode.

src/keyboard.c

@@ -681,6 +681,8 @@ static SIGTYPE interrupt_signal P_ ((int signalnum));
    to support it.  */
 static int cannot_suspend;
 
+extern Lisp_Object Qidentity, Qonly;
+
 /* Install the string STR as the beginning of the string of echoing,
    so that it serves as a prompt for the next character.
    Also start echoing.  */
@@ -1822,6 +1824,16 @@ command_loop_1 ()
 	    call1 (Vrun_hooks, intern ("activate-mark-hook"));
 	}
 
+      /* Setting transient-mark-mode to `only' is a way of
+	 turning it on for just one command.  */
+      if (!NILP (current_buffer->mark_active) && !NILP (Vrun_hooks))
+	{
+	  if (EQ (Vtransient_mark_mode, Qidentity))
+	    Vtransient_mark_mode = Qnil;
+	  if (EQ (Vtransient_mark_mode, Qonly))
+	    Vtransient_mark_mode = Qidentity;
+	}
+
     finalize:
 
       if (current_buffer == prev_buffer