Add a helper function to compare file contents

In the next commit, Git will learn to disallow hooks during `git clone`
operations _except_ when those hooks come from the templates (which are
inherently supposed to be trusted). To that end, we add a function to
compare the contents of two files.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

t/helper/test-path-utils.c

@@ -495,6 +495,16 @@ int cmd__path_utils(int argc, const char **argv)
 		return !!res;
 	}
 
+	if (argc == 4 && !strcmp(argv[1], "do_files_match")) {
+		int ret = do_files_match(argv[2], argv[3]);
+
+		if (ret)
+			printf("equal\n");
+		else
+			printf("different\n");
+		return !ret;
+	}
+
 	fprintf(stderr, "%s: unknown function name: %s\n", argv[0],
 		argv[1] ? argv[1] : "(there was none)");
 	return 1;