Re: [PATCH v3 13/20] unpack-trees: allow sparse directories

> From: Derrick Stolee <dstolee@microsoft.com>
>
> The index_pos_by_traverse_info() currently throws a BUG() when a
> directory entry exists exactly in the index. We need to consider that it
> is possible to have a directory in a sparse index as long as that entry
> is itself marked with the skip-worktree bit.
>
> The 'pos' variable is assigned a negative value if an exact match is not
> found. Since a directory name can be an exact match, it is no longer an
> error to have a nonnegative 'pos' value.
>
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
>  unpack-trees.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/unpack-trees.c b/unpack-trees.c
> index 2da3e5ec77a1..e81d82d72d89 100644
> --- a/unpack-trees.c
> +++ b/unpack-trees.c
> @@ -749,9 +749,12 @@ static int index_pos_by_traverse_info(struct name_entry *names,
>  	strbuf_make_traverse_path(&name, info, names->path, names->pathlen);
>  	strbuf_addch(&name, '/');
>  	pos = index_name_pos(o->src_index, name.buf, name.len);
> -	if (pos >= 0)
> -		BUG("This is a directory and should not exist in index");
> -	pos = -pos - 1;
> +	if (pos >= 0) {
> +		if (!o->src_index->sparse_index ||
> +		    !(o->src_index->cache[pos]->ce_flags & CE_SKIP_WORKTREE))
> +			BUG("This is a directory and should not exist in index");
> +	} else
> +		pos = -pos - 1;