[PATCH v2 2/2] sha1_file: improve sha1_file_name() perfs

[Christian Couder <christian.couder@gmail.com>]

As sha1_file_name() could be performance sensitive, let's
try to make it faster by seeding the initial buffer size
to avoid any need to realloc and by using strbuf_addstr()
and strbuf_addc() instead of strbuf_addf().

Helped-by: Derrick Stolee <stolee@gmail.com>
Helped-by: Jeff Hostetler <git@jeffhostetler.com>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 sha1_file.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sha1_file.c b/sha1_file.c
index f66c21b2da..1a94716962 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -323,8 +323,14 @@ static void fill_sha1_path(struct strbuf *buf, const unsigned char *sha1)
 
 void sha1_file_name(struct strbuf *buf, const unsigned char *sha1)
 {
-	strbuf_addf(buf, "%s/", get_object_directory());
+	const char *obj_dir = get_object_directory();
+	size_t extra = strlen(obj_dir) + 1 + GIT_MAX_HEXSZ;
 
+	if (extra > strbuf_avail(buf))
+		strbuf_grow(buf, extra);
+
+	strbuf_addstr(buf, obj_dir);
+	strbuf_addch(buf, '/');
 	fill_sha1_path(buf, sha1);
 }
 
-- 
2.16.0.rc2.3.g254af8b974