[PATCH 2/2] ls-files: move only kept cache entries in prune_cache()

["René Scharfe" <l.s.r@web.de>]

prune_cache() first identifies those entries at the start of the sorted
array that can be discarded.  Then it moves the rest of the entries up.
Last it identifies the unwanted trailing entries among the moved ones
and cuts them off.

Change the order: Identify both start *and* end of the range to keep
first and then move only those entries to the top.  The resulting code
is slightly shorter and a bit more efficient.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
The performance impact is probably only measurable with a *really* big
index.

 builtin/ls-files.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index 18105ec7ea..1c0f057d02 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -379,10 +379,7 @@ static void prune_cache(const char *prefix, size_t prefixlen)
 	pos = cache_name_pos(prefix, prefixlen);
 	if (pos < 0)
 		pos = -pos-1;
-	memmove(active_cache, active_cache + pos,
-		(active_nr - pos) * sizeof(struct cache_entry *));
-	active_nr -= pos;
-	first = 0;
+	first = pos;
 	last = active_nr;
 	while (last > first) {
 		int next = (last + first) >> 1;
@@ -393,7 +390,9 @@ static void prune_cache(const char *prefix, size_t prefixlen)
 		}
 		last = next;
 	}
-	active_nr = last;
+	memmove(active_cache, active_cache + pos,
+		(last - pos) * sizeof(struct cache_entry *));
+	active_nr = last - pos;
 }
 
 /*
-- 
2.11.1