Introduce struct cgit_context

This struct will hold all the cgit runtime information currently found in
a multitude of global variables.

The first cleanup removes all querystring-related variables.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

ui-refs.c

@@ -16,9 +16,9 @@ void cgit_print_refs()
 
 	html("<table class='list nowrap'>");
 
-	if (cgit_query_path && !strncmp(cgit_query_path, "heads", 5))
+	if (ctx.qry.path && !strncmp(ctx.qry.path, "heads", 5))
 		cgit_print_branches(0);
-	else if (cgit_query_path && !strncmp(cgit_query_path, "tags", 4))
+	else if (ctx.qry.path && !strncmp(ctx.qry.path, "tags", 4))
 		cgit_print_tags(0);
 	else {
 		cgit_print_branches(0);