Here is a patch that I am currently running successfully on my server.

diff --git lib/fetch.c lib/fetch.c
index 3bdd5de6..0e60b215 100644
--- lib/fetch.c
+++ lib/fetch.c
@@ -800,6 +800,15 @@ got_fetch_pack(struct got_object_id **pack_hash, 
struct got_pathlist_head *refs,
         free(tmpidxpath);
         tmpidxpath = NULL;

+       if (chmod(packpath, GOT_DEFAULT_FILE_MODE) != 0) {
+               err = got_error_from_errno2("chmod", packpath);
+               goto done;
+       }
+       if (chmod(idxpath, GOT_DEFAULT_FILE_MODE) != 0) {
+               err = got_error_from_errno2("chmod", idxpath);
+               goto done;
+       }
+
  done:
         if (tmppackpath && unlink(tmppackpath) == -1 && err == NULL)
                 err = got_error_from_errno2("unlink", tmppackpath);