Re: [PATCH 1/6] sequencer: extract helper to update active_cache_tree

> This patch extracts the code from is_index_unchanged() to initialize or
> update the index' cache tree (i.e. a tree object reflecting the current
> index' top-level tree).
>
> The new helper will be used in the upcoming code to support `git rebase
> -i --root` via the sequencer.
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>  sequencer.c | 27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/sequencer.c b/sequencer.c
> index e2f83942843..90c8218aa9a 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -562,9 +562,23 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
>         return !clean;
>  }
>
> +static struct object_id *get_cache_tree_oid(void)
> +{
> +       if (!active_cache_tree)
> +               active_cache_tree = cache_tree();
> +
> +       if (!cache_tree_fully_valid(active_cache_tree))
> +               if (cache_tree_update(&the_index, 0)) {
> +                       error(_("unable to update cache tree"));
> +                       return NULL;
> +               }