Re: [PATCH v7 12/16] diff-lib: handle index diffs with sparse dirs

>
> From: Derrick Stolee <dstolee@microsoft.com>
>
> While comparing an index to a tree, we may see a sparse directory entry.
> In this case, we should compare that portion of the tree to the tree
> represented by that entry. This could include a new tree which needs to
> be expanded to a full list of added files. It could also include an
> existing tree, in which case all of the changes inside are important to
> describe, including the modifications, additions, and deletions. Note
> that the case where the tree has a path and the index does not remains
> identical to before: the lack of a cache entry is the same with a sparse
> index.
>
> Use diff_tree_oid() appropriately to compute the diff.
>
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
>  diff-lib.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/diff-lib.c b/diff-lib.c
> index c2ac9250fe9..3f32f038371 100644
> --- a/diff-lib.c
> +++ b/diff-lib.c
> @@ -325,6 +325,11 @@ static void show_new_file(struct rev_info *revs,
>         unsigned dirty_submodule = 0;
>         struct index_state *istate = revs->diffopt.repo->index;
>
> +       if (new_file && S_ISSPARSEDIR(new_file->ce_mode)) {
> +               diff_tree_oid(NULL, &new_file->oid, new_file->name, &revs->diffopt);
> +               return;
> +       }
> +
>         /*
>          * New file in the index: it might actually be different in
>          * the working tree.
> @@ -347,6 +352,17 @@ static int show_modified(struct rev_info *revs,
>         unsigned dirty_submodule = 0;
>         struct index_state *istate = revs->diffopt.repo->index;
>
> +       /*
> +        * If both are sparse directory entries, then expand the
> +        * modifications to the file level.
> +        */
> +       if (old_entry && new_entry &&
> +           S_ISSPARSEDIR(old_entry->ce_mode) &&
> +           S_ISSPARSEDIR(new_entry->ce_mode)) {
> +               diff_tree_oid(&old_entry->oid, &new_entry->oid, new_entry->name, &revs->diffopt);
> +               return 0;
> +       }
> +
>         if (get_stat_data(istate, new_entry, &oid, &mode, cached, match_missing,
>                           &dirty_submodule, &revs->diffopt) < 0) {
>                 if (report_missing)