Support for excluding variable from forwarding via forward_variables_form.

tools/gn/docs/reference.md

Index: tools/gn/docs/reference.md
diff --git a/tools/gn/docs/reference.md b/tools/gn/docs/reference.md
index 97f12f21e1f531d378f612a2d11316798d7e5e7c..9cc04025f30033cdbf55614b4d74ffb390ffd992 100644
--- a/tools/gn/docs/reference.md
+++ b/tools/gn/docs/reference.md
@@ -1329,6 +1329,9 @@
 ```
   forward_variables_from(from_scope, variable_list_or_star)
 
+  forward_variables_from(from_scope, variable_list_or_star,
+                         variable_to_not_forward_list)
+
   Copies the given variables from the given scope to the local scope
   if they exist. This is normally used in the context of templates to
   use the values of variables defined in the template invocation to
@@ -1354,6 +1357,9 @@
   is never applied by this function. It's assumed than any desired
   filtering was already done when sources was set on the from_scope.
 
+  The second form of the function allows to give a list of variables not
+  to forward. This is mostly useful when used in combination with "*".
+
 ```
 
 ### **Examples**
@@ -1383,7 +1389,19 @@
     target(my_wrapper_target_type, target_name) {
       forward_variables_from(invoker, "*")
     }
- }
+  }
+
+  # This is a template around another template that uses a variable to
+  # initialize another variable and is only interested in that one.
+  template("my_ios_test_app") {
+    ios_test_app(target_name) {
+      forward_variables_from(invoker, "*", ["test_bundle_name"])
+      if (!defined(extra_substitutions)) {
+        extra_substitutions = []
+      }
+      extra_substitutions += [ "BUNDLE_ID_TEST_NAME=$test_bundle_name" ]
+    }
+  }
 
 
 ```