Re: [PATCH v3 5/6] stash: apply stash using 'merge_ort_nonrecursive()'

> diff --git a/builtin/stash.c b/builtin/stash.c
> index 1bfba532044..3fe549f7d3c 100644
> --- a/builtin/stash.c
> +++ b/builtin/stash.c
> @@ -492,13 +493,13 @@ static void unstage_changes_unless_new(struct object_id *orig_tree)
>  static int do_apply_stash(const char *prefix, struct stash_info *info,
>  			  int index, int quiet)
>  {
> -	int ret;
> +	int clean, ret;
>  	int has_index = index;
>  	struct merge_options o;
>  	struct object_id c_tree;
>  	struct object_id index_tree;
> -	struct commit *result;
> -	const struct object_id *bases[1];
> +	struct tree *head, *merge, *merge_base;
> +	struct lock_file lock = LOCK_INIT;
>  
>  	read_cache_preload(NULL);
>  	if (refresh_and_write_cache(REFRESH_QUIET, 0, 0))
> @@ -541,6 +542,7 @@ static int do_apply_stash(const char *prefix, struct stash_info *info,
>  
>  	o.branch1 = "Updated upstream";
>  	o.branch2 = "Stashed changes";
> +	o.ancestor = "Stash base";
>  
>  	if (oideq(&info->b_tree, &c_tree))
>  		o.branch1 = "Version stash was based on";
> @@ -551,10 +553,26 @@ static int do_apply_stash(const char *prefix, struct stash_info *info,
>  	if (o.verbosity >= 3)
>  		printf_ln(_("Merging %s with %s"), o.branch1, o.branch2);
>  
> -	bases[0] = &info->b_tree;
> +	head = lookup_tree(o.repo, &c_tree);
> +	merge = lookup_tree(o.repo, &info->w_tree);
> +	merge_base = lookup_tree(o.repo, &info->b_tree);
> +
> +	repo_hold_locked_index(o.repo, &lock, LOCK_DIE_ON_ERROR);
> +	clean = merge_ort_nonrecursive(&o, head, merge, merge_base);
> +
> +	/*
> +	 * If 'clean' >= 0, reverse the value for 'ret' so 'ret' is 0 when the
> +	 * merge was clean, and nonzero if the merge was unclean or encountered
> +	 * an error.
> +	 */
> +	ret = clean >= 0 ? !clean : clean;
> +
> +	if (ret < 0)
> +		rollback_lock_file(&lock);
> +	else if (write_locked_index(o.repo->index, &lock,
> +				      COMMIT_LOCK | SKIP_IF_UNCHANGED))
> +		ret = error(_("could not write index"));
>  
> -	ret = merge_recursive_generic(&o, &c_tree, &info->w_tree, 1, bases,
> -				      &result);

> diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
> index 85c6a56f1b7..aaf4d880dbc 100755
> --- a/t/t1092-sparse-checkout-compatibility.sh
> +++ b/t/t1092-sparse-checkout-compatibility.sh
> @@ -1385,7 +1385,7 @@ test_expect_success 'sparse-index is not expanded: stash' '
>  	ensure_not_expanded stash &&
>  	ensure_not_expanded stash list &&
>  	ensure_not_expanded stash show stash@{0} &&
> -	! ensure_not_expanded stash apply stash@{0} &&
> +	ensure_not_expanded stash apply stash@{0} &&
>  	ensure_not_expanded stash drop stash@{0} &&
>  
>  	echo >>sparse-index/deep/new &&
> @@ -1399,7 +1399,7 @@ test_expect_success 'sparse-index is not expanded: stash' '
>  	oid=$(git -C sparse-index stash create) &&
>  	ensure_not_expanded stash store -m "test" $oid &&
>  	ensure_not_expanded reset --hard &&
> -	! ensure_not_expanded stash pop
> +	ensure_not_expanded stash pop
>  '
>  
>  test_expect_success 'sparse index is not expanded: diff' '