[PATCH] cache-tree: remove use of strbuf_addf in update_one

[Kevin Willford <kcwillford@gmail.com>]

String formatting can be a performance issue when there are
hundreds of thousands of trees.

Change to stop using the strbuf_addf and just add the strings
or characters individually.

There are a limited number of modes so added a switch for the
known ones and a default case if something comes through that
are not a known one for git.

Signed-off-by: Kevin Willford <kewillf@microsoft.com>
---
 cache-tree.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/cache-tree.c b/cache-tree.c
index 2440d1dc89..41744b3db7 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -390,7 +390,29 @@ static int update_one(struct cache_tree *it,
 			continue;
 
 		strbuf_grow(&buffer, entlen + 100);
-		strbuf_addf(&buffer, "%o %.*s%c", mode, entlen, path + baselen, '\0');
+
+		switch (mode) {
+		case 0100644:
+			strbuf_add(&buffer, "100644 ", 7);
+			break;
+		case 0100664:
+			strbuf_add(&buffer, "100664 ", 7);
+			break;
+		case 0100755:
+			strbuf_add(&buffer, "100755 ", 7);
+			break;
+		case 0120000:
+			strbuf_add(&buffer, "120000 ", 7);
+			break;
+		case 0160000:
+			strbuf_add(&buffer, "160000 ", 7);
+			break;
+		default:
+			strbuf_addf(&buffer, "%o ", mode);
+			break;
+		}
+		strbuf_add(&buffer, path + baselen, entlen);
+		strbuf_addch(&buffer, '\0');
 		strbuf_add(&buffer, sha1, 20);
 
 #if DEBUG
-- 
2.14.0.rc0.286.g44127d70e4