html: html_ntxt with no ellipsis

For implementing a ui-blame page, there is need for a function that
outputs a selection from a block of text, transformed for HTML output,
but with no further modifications or additions.

Signed-off-by: Jeff Smith <whydoubt@gmail.com>
Reviewed-by: John Keeping <john@keeping.me.uk>
diff --git a/ui-repolist.c b/ui-repolist.c
index 7272e87..af52f9b 100644
--- a/ui-repolist.c
+++ b/ui-repolist.c
@@ -329,7 +329,8 @@
 		repourl = cgit_repourl(ctx.repo->url);
 		html_link_open(repourl, NULL, NULL);
 		free(repourl);
-		html_ntxt(ctx.cfg.max_repodesc_len, ctx.repo->desc);
+		if (html_ntxt(ctx.repo->desc, ctx.cfg.max_repodesc_len) < 0)
+			html("...");
 		html_link_close();
 		html("</td><td>");
 		if (ctx.cfg.enable_index_owner) {