Re: [RFC/PATCH] worktree: replace "checkout --to" with "worktree new"

> On Thu, Jul 2, 2015 at 7:41 PM, Duy Nguyen <pclouds@gmail.com> wrote:
>>> merge_working_tree:
>>>     tree = parse_tree_indirect(old->commit &&
>>>         !opts->new_worktree_mode ?
>>>             old->commit->object.sha1 :
>>>             EMPTY_TREE_SHA1_BIN);
>>
>> I think it's to make sure empty sha-1 is used with --to. If
>> old->commit->object.sha1 is used and it's something, a real two way
>> merge may happen probably with not-so-fun consequences. If it's empty
>> sha1, the effect is like "reset --hard", silent and reliable..
>>
>>> switch_branches:
>>>     if (!opts->quiet && !old.path && old.commit &&
>>>         new->commit != old.commit && !opts->new_worktree_mode)
>>>             orphaned_commit_warning(old.commit, new->commit);
>>
>> to suppress misleading warning if old.commit happens to be something.
>
> Actually you may be right about not reverting these. We prepare the
> new worktree with a valid HEAD, that would make "old" valid and may
> trigger things if "git checkout" is used to populate the worktree. To
> suppress those "things", we need new_worktree_mode or something
> similar.

> Unless we want to borrow fancy checkout options for "git worktree
> add", we probably should just export checkout() function from clone.c
> and use it instead of "git checkout". Much more lightweight and
> simpler (it's one-way merge). Then we can revert checkout.c to the
> version before "--to".