ui-plain: fix to show a repo's root directory listing in plain view

This is to fix the case of accessing http://host.com/cgit.cgi/repo.git/plain/

There is code here to make this case work (match_baselen is set to -1
for top-of-the-tree views) but the unsigned to signed comparison was
always false in this case, causing an empty directory listing without
this fix.

Signed-off-by: Joe Anakata <jea-signup-github@anakata.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

ui-plain.c

@@ -143,7 +143,7 @@ static int walk_tree(const unsigned char *sha1, struct strbuf *base,
 			walk_tree_ctx->match = 2;
 			return READ_TREE_RECURSIVE;
 		}
-	} else if (base->len > walk_tree_ctx->match_baselen) {
+	} else if (base->len < INT_MAX && (int)base->len > walk_tree_ctx->match_baselen) {
 		print_dir_entry(sha1, base->buf, base->len, pathname, mode);
 		walk_tree_ctx->match = 2;
 	} else if (S_ISDIR(mode)) {