[PATCH] index-pack: do not segfault when keep_name is NULL

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

keep_name is used to print error messages a couple lines down. Reset
it to the real path returned by odb_pack_keep() if it's set to NULL by
caller.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 One of these moments I will make git log and friends optionally recognize
 "Diff-Options:" line in commit message. Adding -U14 in this case
 should help the reviewer to see how those error messages are printed.

 builtin/index-pack.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index a6b1c17..d95c3dc 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -1283,9 +1283,10 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 	if (keep_msg) {
 		int keep_fd, keep_msg_len = strlen(keep_msg);
 
-		if (!keep_name)
+		if (!keep_name) {
 			keep_fd = odb_pack_keep(name, sizeof(name), sha1);
-		else
+			keep_name = name;
+		} else
 			keep_fd = open(keep_name, O_RDWR|O_CREAT|O_EXCL, 0600);
 
 		if (keep_fd < 0) {
-- 
1.9.0.40.gaa8c3ea