Add test case for ls-files --with-tree

This tests basic functionality and also exercises a bug noticed
by Keith Packard, (prune_cache followed by add_index_entry can
trigger an attempt to realloc a pointer into the middle of an
allocated buffer).

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3060-ls-files-with-tree.sh

@@ -0,0 +1,71 @@
+#!/bin/sh
+#
+# Copyright (c) 2007 Carl D. Worth
+#
+
+test_description='git ls-files test (--with-tree).
+
+This test runs git ls-files --with-tree and in particular in
+a scenario known to trigger a crash with some versions of git.
+'
+. ./test-lib.sh
+
+test_expect_success setup '
+
+	# The bug we are exercising requires a fair number of entries
+	# in a sub-directory so that add_index_entry will trigger a
+	# realloc.
+
+	echo file >expected &&
+	mkdir sub &&
+	bad= &&
+	for n in 0 1 2 3 4 5
+	do
+		for m in 0 1 2 3 4 5 6 7 8 9
+		do
+			num=00$n$m &&
+			>sub/file-$num &&
+			echo file-$num >>expected || {
+				bad=t
+				break
+			}
+		done && test -z "$bad" || {
+			bad=t
+			break
+		}
+	done && test -z "$bad" &&
+	git add . &&
+	git commit -m "add a bunch of files" &&
+
+	# We remove them all so that we will have something to add
+	# back with --with-tree and so that we will definitely be
+	# under the realloc size to trigger the bug.
+	rm -rf sub &&
+	git commit -a -m "remove them all" &&
+
+	# The bug also requires some entry before our directory so that
+	# prune_path will modify the_index.cache
+
+	mkdir a_directory_that_sorts_before_sub &&
+	>a_directory_that_sorts_before_sub/file &&
+	mkdir sub &&
+	>sub/file &&
+	git add .
+'
+
+# We have to run from a sub-directory to trigger prune_path
+# Then we finally get to run our --with-tree test
+cd sub
+
+test_expect_success 'git -ls-files --with-tree should succeed from subdir' '
+
+	git ls-files --with-tree=HEAD~1 >../output
+
+'
+
+cd ..
+test_expect_success \
+    'git -ls-files --with-tree should add entries from named tree.' \
+    'diff -u expected output'
+
+test_done