Merge branch 'ls/clean-smudge-override-in-config'

Clean/smudge filters defined in a configuration file of lower
precedence can now be overridden to be a pass-through no-op by
setting the variable to an empty string.

* ls/clean-smudge-override-in-config:
  convert: treat an empty string for clean/smudge filters as "cat"

convert.c

@@ -434,7 +434,7 @@ static int apply_filter(const char *path, const char *src, size_t len, int fd,
 	struct async async;
 	struct filter_params params;
 
-	if (!cmd)
+	if (!cmd || !*cmd)
 		return 0;
 
 	if (!dst)

t/t0021-conversion.sh

@@ -252,4 +252,20 @@ test_expect_success "filter: smudge empty file" '
 	test_cmp expected filtered-empty-in-repo
 '
 
+test_expect_success 'disable filter with empty override' '
+	test_config_global filter.disable.smudge false &&
+	test_config_global filter.disable.clean false &&
+	test_config filter.disable.smudge false &&
+	test_config filter.disable.clean false &&
+
+	echo "*.disable filter=disable" >.gitattributes &&
+
+	echo test >test.disable &&
+	git -c filter.disable.clean= add test.disable 2>err &&
+	test_must_be_empty err &&
+	rm -f test.disable &&
+	git -c filter.disable.smudge= checkout -- test.disable 2>err &&
+	test_must_be_empty err
+'
+
 test_done