diff-lib: stop calling diff_setup_done() in do_diff_cache()
d44e5267ea (diff-lib: plug minor memory leaks in do_diff_cache(),
2020-11-14) added the call to diff_setup_done() to release the memory
of the parseopt member of struct diff_options that repo_init_revisions()
had allocated via repo_diff_setup() and prep_parse_options().
189e97bc4b (diff: remove parseopts member from struct diff_options,
2022-12-01) did away with that allocation; diff_setup_done() doesn't
release any memory anymore. So stop calling this function on the blank
diffopt member before it is overwritten, as this is no longer necessary.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>