Return http statuscode 404 on unknown branch

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

cgit.c

@@ -285,6 +285,8 @@ static int prepare_repo_cmd(struct cgit_context *ctx)
 	if (get_sha1(ctx->qry.head, sha1)) {
 		tmp = xstrdup(ctx->qry.head);
 		ctx->qry.head = ctx->repo->defbranch;
+		ctx->page.status = 404;
+		ctx->page.statusmsg = "not found";
 		cgit_print_http_headers(ctx);
 		cgit_print_docstart(ctx);
 		cgit_print_pageheader(ctx);

cgit.h

@@ -181,6 +181,8 @@ struct cgit_page {
 	char *charset;
 	char *filename;
 	char *title;
+	int status;
+	char *statusmsg;
 };
 
 struct cgit_context {

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)
 {
+	if (ctx->page.status)
+		htmlf("Status: %d %s\n", ctx->page.status, ctx->page.statusmsg);
 	if (ctx->page.mimetype && ctx->page.charset)
 		htmlf("Content-Type: %s; charset=%s\n", ctx->page.mimetype,
 		      ctx->page.charset);