tools: add import comments.

Change-Id: Idda6e64580432cb9a731e4ebf4005ee4ceb4202d
Reviewed-on: https://go-review.googlesource.com/1244
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/refactor/importgraph/graph.go b/refactor/importgraph/graph.go
index 777fee8..6f49fab 100644
--- a/refactor/importgraph/graph.go
+++ b/refactor/importgraph/graph.go
@@ -4,7 +4,7 @@
 
 // Package importgraph computes the forward and reverse import
 // dependency graphs for all packages in a Go workspace.
-package importgraph
+package importgraph // import "golang.org/x/tools/refactor/importgraph"
 
 import (
 	"go/build"