delay progress display when checking out files

Let's start displaying progress only if more than 50% of total number
of files remains to be checked out after 2 seconds.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/unpack-trees.c b/unpack-trees.c
index cefc404..675a999 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -304,13 +304,8 @@
 				total++;
 		}
 
-		/* Don't bother doing this for very small updates */
-		if (total < 250)
-			total = 0;
-
-		if (total)
-			start_progress(&progress, "Checking %u files out...",
-				       "", total);
+		start_progress_delay(&progress, "Checking %u files out...",
+				     "", total, 50, 2);
 		cnt = 0;
 	}