patch 7.4.1712
Problem:    For plugins in packages, plugin authors need to take care of all
            dependencies.
Solution:   When loading "start" packages and for :packloadall, first add all
            directories to 'runtimepath' before sourcing plugins.
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 9f74376..657c772 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -3313,6 +3313,11 @@
     }
 }
 
+/* used for "cookie" of add_pack_plugin() */
+static int APP_ADD_DIR;
+static int APP_LOAD;
+static int APP_BOTH;
+
     static void
 add_pack_plugin(char_u *fname, void *cookie)
 {
@@ -3324,11 +3329,10 @@
     int	    oldlen;
     int	    addlen;
     char_u  *ffname = fix_fname(fname);
-    int	    load_files = cookie != NULL;
 
     if (ffname == NULL)
 	return;
-    if (strstr((char *)p_rtp, (char *)ffname) == NULL)
+    if (cookie != &APP_LOAD && strstr((char *)p_rtp, (char *)ffname) == NULL)
     {
 	/* directory not in 'runtimepath', add it */
 	p4 = p3 = p2 = p1 = get_past_head(ffname);
@@ -3374,7 +3378,7 @@
 	vim_free(new_rtp);
     }
 
-    if (load_files)
+    if (cookie != &APP_ADD_DIR)
     {
 	static char *plugpat = "%s/plugin/**/*.vim";
 	static char *ftpat = "%s/ftdetect/*.vim";
@@ -3423,8 +3427,14 @@
     if (!did_source_packages || (eap != NULL && eap->forceit))
     {
 	did_source_packages = TRUE;
+
+	/* First do a round to add all directories to 'runtimepath', then load
+	 * the plugins. This allows for plugins to use an autoload directory
+	 * of another plugin. */
 	do_in_path(p_pp, (char_u *)"pack/*/start/*", DIP_ALL + DIP_DIR,
-							add_pack_plugin, p_pp);
+					       add_pack_plugin, &APP_ADD_DIR);
+	do_in_path(p_pp, (char_u *)"pack/*/start/*", DIP_ALL + DIP_DIR,
+						  add_pack_plugin, &APP_LOAD);
     }
 }
 
@@ -3444,7 +3454,7 @@
 	return;
     vim_snprintf(pat, len, plugpat, eap->arg);
     do_in_path(p_pp, (char_u *)pat, DIP_ALL + DIP_DIR + DIP_ERR,
-				 add_pack_plugin, eap->forceit ? NULL : p_pp);
+		    add_pack_plugin, eap->forceit ? &APP_ADD_DIR : &APP_BOTH);
     vim_free(pat);
 }