Re: [PATCH v2 18/23] checkout: retire --to option

> Now that "git worktree add" has achieved user-facing feature-parity with
> "git checkout --to", retire the latter.
>
> Move the actual linked worktree creation functionality,
> prepare_linked_checkout() and its helpers, verbatim from checkout.c to
> worktree.c.
>
> This effectively reverts changes to checkout.c by 529fef2 (checkout:
> support checking out into a new working directory, 2014-11-30) with the
> exception of merge_working_tree() and switch_branches() which still
> require specialized knowledge that a the checkout is occurring in a
> newly-created linked worktree (signaled to them by the private
> GIT_CHECKOUT_NEW_WORKTREE environment variable).
>
> Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
> ---
>  builtin/checkout.c | 156 +----------------------------------------------------
>  builtin/worktree.c | 138 ++++++++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 133 insertions(+), 161 deletions(-)