commit-graph: compute generation numbers

diff --git a/builtin/log.c b/builtin/log.c
index 46b4ca13e5c11ff43c15d80e618914e671ff17a0..f4d30d2f3da84f9f18de4fbf16ada6f96c9cb836 100644 (file)
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1064,8 +1064,8 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 
        diff_setup_done(&opts);
 
-       diff_tree_oid(&origin->tree->object.oid,
-                     &head->tree->object.oid,
+       diff_tree_oid(get_commit_tree_oid(origin),
+                     get_commit_tree_oid(head),
                      "", &opts);
        diffcore_std(&opts);
        diff_flush(&opts);