diff --git a/misc/pre-commit.githook b/misc/pre-commit.githook
index f9fd2d36b..c0fe8f0f4 100755
--- a/misc/pre-commit.githook
+++ b/misc/pre-commit.githook
@@ -1,6 +1,22 @@
 #!/usr/bin/env sh
 
 exitstatus=0
+
+#third_party imports.
+cd third_party
+rewrite=`./rewrite-imports.sh -l`
+cd ..
+if [ -n "$rewrite" ]
+then
+	exitstatus=1
+	for r in $rewrite
+	do
+		echo $r
+	done
+	echo "The above need their imports to be fixed. Use rewrite-imports.sh -w"
+fi
+
+#gofmt and trailing space errors
 committed=`git diff-index --cached --name-only HEAD`
 for c in $committed
 do
diff --git a/third_party/rewrite-imports.sh b/third_party/rewrite-imports.sh
index 4cd6d2182..e2d0d93fb 100755
--- a/third_party/rewrite-imports.sh
+++ b/third_party/rewrite-imports.sh
@@ -1,7 +1,21 @@
 #!/bin/sh
 
-find . -type f -name '*.go' -exec perl -pi -e 's!"code.google.com/!"camlistore.org/third_party/code.google.com/!' {} \;
-find . -type f -name '*.go' -exec perl -pi -e 's!"launchpad.net/!"camlistore.org/third_party/launchpad.net/!' {} \;
-find . -type f -name '*.go' -exec perl -pi -e 's!"github.com/!"camlistore.org/third_party/github.com/!' {} \;
-find . -type f -name '*.go' -exec perl -pi -e 's!"labix.org/!"camlistore.org/third_party/labix.org/!' {} \;
-
+if [ "$1" = "-l" ]
+then
+	find . -type f -name '*.go' -exec grep -E -l '"code.google.com/' {} \;
+	find . -type f -name '*.go' -exec grep -E -l '"launchpad.net/' {} \;
+	find . -type f -name '*.go' -exec grep -E -l '"github.com/' {} \;
+	find . -type f -name '*.go' -exec grep -E -l '"labix.org/' {} \;
+elif [ "$1" = "-w" ]
+then
+	find . -type f -name '*.go' -exec perl -pi -e 's!"code.google.com/!"camlistore.org/third_party/code.google.com/!' {} \;
+	find . -type f -name '*.go' -exec perl -pi -e 's!"launchpad.net/!"camlistore.org/third_party/launchpad.net/!' {} \;
+	find . -type f -name '*.go' -exec perl -pi -e 's!"github.com/!"camlistore.org/third_party/github.com/!' {} \;
+	find . -type f -name '*.go' -exec perl -pi -e 's!"labix.org/!"camlistore.org/third_party/labix.org/!' {} \;
+else
+	cat << heredoc
+usage: rewrite-imports.sh -l|-w"
+	-l: list files where a rewrite is needed"
+	-w: actually performs the rewrite"
+heredoc
+fi