patch 8.2.1398: autoload script sourced twice if sourced directly

Problem:    Autoload script sourced twice if sourced directly.
Solution:   Do not source an autoload script again. (issue #6644)

Author: brammool

src/scriptfile.c

@@ -2012,6 +2012,7 @@ script_autoload(
     char_u	*scriptname, *tofree;
     int		ret = FALSE;
     int		i;
+    int		ret_sid;
 
     // If there is no '#' after name[0] there is no package name.
     p = vim_strchr(name, AUTOLOAD_CHAR);
@@ -2039,7 +2040,8 @@ script_autoload(
 	}
 
 	// Try loading the package from $VIMRUNTIME/autoload/<name>.vim
-	if (source_runtime(scriptname, 0) == OK)
+	// Use "ret_sid" to avoid loading the same script again.
+	if (source_in_path(p_rtp, scriptname, 0, &ret_sid) == OK)
 	    ret = TRUE;
     }
 

src/testdir/sautest/autoload/sourced.vim

@@ -1,3 +1,4 @@
 let g:loaded_sourced_vim += 1
-func! sourced#something()
+func sourced#something()
 endfunc
+call sourced#something()

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1398,
 /**/
     1397,
 /**/