checkout: drop 'checkout_opts' dependency from prepare_linked_checkout
The plan is to relocate "git checkout --to" functionality to "git
worktree add", however, worktree.c won't have access to the 'struct
checkout_opts' passed to prepare_linked_worktree(), which it consults
for the pathname of the new worktree and the argv[] of the command it
should run to populate the new worktree. Facilitate relocation of
prepare_linked_worktree() by instead having it accept the pathname and
argv[] directly, thus eliminating the final references to 'struct
checkout_opts'.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>