diff --git a/git-filter-branch.sh b/git-filter-branch.sh
old mode 100755
new mode 100644
index bfd118cd3ba070bbcc611be4c8d6adcd2a4d294a..8fa5ce6467b12119868a4c3c74c3e3740f6d6b8e
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -178,6 +178,14 @@
 #
 #	git-filter-branch ... new-H C..H --not D
 #	git-filter-branch ... new-H D..H --not C
+#
+# To move the whole tree into a subdirectory, or remove it from there:
+#
+# git-filter-branch --index-filter \
+#	'git-ls-files -s | sed "s-\t-&newsubdir/-" |
+#		GIT_INDEX_FILE=$GIT_INDEX_FILE.new \
+#			git-update-index --index-info &&
+#	 mv $GIT_INDEX_FILE.new $GIT_INDEX_FILE' directorymoved
 
 # Testsuite: TODO
 
diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh
index 0fabe4904f7bfb942ba24287862d054e9a4d174c..f00c262e450f9ba23b8e065bce2e4780185821af 100755
--- a/t/t7003-filter-branch.sh
+++ b/t/t7003-filter-branch.sh
@@ -99,4 +99,12 @@ test_expect_success 'subdirectory filter result looks okay' '
 	! git show sub:subdir
 '
 
+test_expect_success 'use index-filter to move into a subdirectory' '
+	git-filter-branch --index-filter \
+		 "git-ls-files -s | sed \"s-\\t-&newsubdir/-\" |
+	          GIT_INDEX_FILE=\$GIT_INDEX_FILE.new \
+			git-update-index --index-info &&
+		  mv \$GIT_INDEX_FILE.new \$GIT_INDEX_FILE" directorymoved &&
+	test -z "$(git diff HEAD directorymoved:newsubdir)"'
+
 test_done