Something I missed when eyeballing this in my just-sent review, here we
have a "revs->repo" already, so let's not fall back on "the_repository",
but use it. I think you want this as a fix-up:
diff --git a/diff-lib.c b/diff-lib.c
index 925d64ff58c..ec8a0f98085 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -312,7 +312,8 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
unsigned long parallel_jobs;
struct string_list_item *item;
- if (git_config_get_ulong("submodule.diffjobs", ¶llel_jobs))
+ if (repo_config_get_ulong(revs->repo, "submodule.diffjobs",
+ ¶llel_jobs))
parallel_jobs = 1;
else if (!parallel_jobs)
parallel_jobs = online_cpus();