Add a test for checking whether gitattributes is honored by checkout.

The original bug will not honor new entries in gitattributes if they
are changed in the same checkout as the files they affect.

It will also keep using .gitattributes, even if it is deleted in the
same commit as the files it affects.

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

t/t0020-crlf.sh

@@ -429,6 +429,37 @@ test_expect_success 'in-tree .gitattributes (4)' '
 	}
 '
 
+test_expect_success 'checkout with existing .gitattributes' '
+
+	git config core.autocrlf true &&
+	git config --unset core.safecrlf &&
+	echo ".file2 -crlfQ" | q_to_cr >> .gitattributes &&
+	git add .gitattributes &&
+	git commit -m initial &&
+	echo ".file -crlfQ" | q_to_cr >> .gitattributes &&
+	echo "contents" > .file &&
+	git add .gitattributes .file &&
+	git commit -m second &&
+
+	git checkout master~1 &&
+	git checkout master &&
+	test "$(git diff-files --raw)" = ""
+
+'
+
+test_expect_success 'checkout when deleting .gitattributes' '
+
+	git rm .gitattributes &&
+	echo "contentsQ" | q_to_cr > .file2 &&
+	git add .file2 &&
+	git commit -m third
+
+	git checkout master~1 &&
+	git checkout master &&
+	remove_cr .file2 >/dev/null
+
+'
+
 test_expect_success 'invalid .gitattributes (must not crash)' '
 
 	echo "three +crlf" >>.gitattributes &&