I need this in my tree, especially the second part, to not break
everything horribly when extending the got_object_id struct.  The
fileindex and worktree code (at least) are not yet ready for sha256, but
this allows them to continue working, at least in my testing.

The first part is to not break gotd.  There are several places in gotd
where we just copy stuff in/out the sha1 buffer, and those should also
continue to work.  (sha256 in the network protocol is pretty down the
todo list :/)

ok?

diff /home/op/w/got
commit - 03a62f6dd737910257cd4602766adca863cc8811
path + /home/op/w/got
blob - 6c9c61a414a0d5c844ce86e60e9544b213cd637c
file + gotd/session_write.c
--- gotd/session_write.c
+++ gotd/session_write.c
@@ -696,7 +696,9 @@ update_ref(int *shut, struct gotd_session_client *clie
 
 	log_debug("updating ref %s for uid %d", refname, client->euid);
 
+	memset(&old_id, 0, sizeof(old_id));
 	memcpy(old_id.sha1, iref.old_id, SHA1_DIGEST_LENGTH);
+	memset(&new_id, 0, sizeof(new_id));
 	memcpy(new_id.sha1, iref.new_id, SHA1_DIGEST_LENGTH);
 	err = got_repo_find_object_id(iref.delete_ref ? &old_id : &new_id,
 	    repo);
blob - e4574472a88375bfac44ed049b2e5050ad77a389
file + lib/object_qid.c
--- lib/object_qid.c
+++ lib/object_qid.c
@@ -31,7 +31,7 @@
 const struct got_error *
 got_object_qid_alloc_partial(struct got_object_qid **qid)
 {
-	*qid = malloc(sizeof(**qid));
+	*qid = calloc(1, sizeof(**qid));
 	if (*qid == NULL)
 		return got_error_from_errno("malloc");