Add support for HEAD requests

This is a quick 'n dirty hack which makes cgit honor HEAD requests.

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

ui-shared.c

@@ -456,6 +456,8 @@ void cgit_print_age(time_t t, time_t max_relative, char *format)
 
 void cgit_print_http_headers(struct cgit_context *ctx)
 {
+	const char *method = getenv("REQUEST_METHOD");
+
 	if (ctx->page.mimetype && ctx->page.charset)
 		htmlf("Content-Type: %s; charset=%s\n", ctx->page.mimetype,
 		      ctx->page.charset);
@@ -471,6 +473,8 @@ void cgit_print_http_headers(struct cgit_context *ctx)
 	if (ctx->page.etag)
 		htmlf("ETag: \"%s\"\n", ctx->page.etag);
 	html("\n");
+	if (method && !strcmp(method, "HEAD"))
+		exit(0);
 }
 
 void cgit_print_docstart(struct cgit_context *ctx)