This is sort of a companion patch to 4723ee9(Close files opened by lock_file() before unlinking.): on Windows, you cannot delete what is still open.
This makes test 9300-fast-import pass on Windows for me; quite a few fast-imports leave temporary packs until the test "blank lines not necessary after other commands" actually tests for the number of files in .git/objects/pack/, which has a few temporary packs now.
I guess that 8b4eb6b(Do not perform cross-directory renames when creating packs) was "responsible" for the breakage.
Signed-off-by: Johannes Schindelin <email@example.com> Signed-off-by: Junio C Hamano <firstname.lastname@example.org>