t0021-conversion.sh: Test that the clean filter really cleans content.

This test uses a rot13 filter, which is its own inverse. It tested only
that the content was the same as the original after both the 'clean' and
the 'smudge' filter were applied. This way it would not detect whether
any filter was run at all. Hence, here we add another test that checks
that the repository contained content that was processed by the 'clean'
filter.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

t/t0021-conversion.sh

@@ -42,7 +42,12 @@ test_expect_success check '
 	git diff --raw --exit-code :test :test.i &&
 	id=$(git rev-parse --verify :test) &&
 	embedded=$(sed -ne "$script" test.i) &&
-	test "z$id" = "z$embedded"
+	test "z$id" = "z$embedded" &&
+
+	git cat-file blob :test.t > test.r &&
+
+	./rot13.sh < test.o > test.t &&
+	cmp test.r test.t
 '
 
 # If an expanded ident ever gets into the repository, we want to make sure that