cgit_open_filter: also take the repo as a parameter

To prepare for handing repo configuration to the
filter script that is executed.

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

ui-repolist.c

@@ -291,7 +291,7 @@ void cgit_print_site_readme()
 	if (!ctx.cfg.root_readme)
 		return;
 	if (ctx.cfg.about_filter)
-		cgit_open_filter(ctx.cfg.about_filter);
+		cgit_open_filter(ctx.cfg.about_filter, NULL);
 	html_include(ctx.cfg.root_readme);
 	if (ctx.cfg.about_filter)
 		cgit_close_filter(ctx.cfg.about_filter);