builtin/pack-objects.c: don't leak memory via arguments

When constructing arguments to pass to setup_revision(), pack-objects only frees the memory used by that array after calling get_object_list(). Ensure that we call strvec_clear() whether or not we use the arguments array by cleaning up whenever we exit the function (and rewriting one early return to jump to a label which frees the memory and then returns). We could avoid setting this array up altogether unless we are in the if-else block that calls get_object_list(), but setting up the argument array is intermingled with lots of other side-effects, e.g.: if (exclude_promisor_objects) { use_internal_rev_list = 1; fetch_if_missing = 0; strvec_push(&rp, "--exclude-promisor-objects"); } So it would be awkward to check exclude_promisor_objects twice: first to set use_internal_rev_list and fetch_if_missing, and then again above get_object_list() to push the relevant argument onto the array. Instead, leave the array's construction alone and make sure to free it unconditionally. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>