bulk-checkin: fix leaking state TODO
When flushing a bulk-checking to disk we also reset the `struct
bulk_checkin_packfile` state. But while we free some of its members,
others aren't being free'd, leading to memory leaks:
- The temporary packfile name is not getting freed.
- The `struct hashfile` only gets freed in case we end up calling
`finalize_hashfile()`. There are code paths though where that is not
the case, namely when nothing has been written. For this, we need to
make `free_hashfile()` public.
Fix those leaks.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>