mv: check if <destination> is a SKIP_WORKTREE_DIR
Originally, <destination> is assumed to be in the working tree. If it is not found as a directory, then it is determined to be either a regular file path, or error out if used under the second form (move into a directory) of 'git-mv'. Such behavior is not ideal, mainly because Git does not look into the index for <destination>, which could potentially be a SKIP_WORKTREE_DIR, which we need to determine for the later "moving from in-cone to out-of-cone" patch. Change the logic so that Git first check if <destination> is a directory with all its contents sparsified (a SKIP_WORKTREE_DIR). If <destination> is such a sparse directory, then we should modify the index the same way as we would if this were a non-sparse directory. We must be careful to ensure that the <destination> is marked with SKIP_WORKTREE_DIR. Also add a `dst_w_slash` to reuse the result from `add_slash()`, which was everywhere and can be simplified. Helped-by: Derrick Stolee <derrickstolee@github.com> Helped-by: Victoria Dye <vdye@github.com> Signed-off-by: Shaoxuan Yuan <shaoxuan.yuan02@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>