Merge branch 'rs/move-array'

Code clean-up.

* rs/move-array:
ls-files: don't try to prune an empty index
apply: use COPY_ARRAY and MOVE_ARRAY in update_image()
use MOVE_ARRAY
add MOVE_ARRAY

diff --cc apply.c
Simple merge

diff --cc commit.c
Simple merge

diff --cc git-compat-util.h
Simple merge