Merge branch 'rs/apply-symlinks-use-strset'

"git apply" (ab)used the util pointer of the string-list to keep
track of how each symbolic link needs to be handled, which has been
simplified by using strset.

* rs/apply-symlinks-use-strset:
  apply: use strsets to track symlinks

diff --cc apply.c
Simple merge

diff --cc apply.h
Simple merge