Merge branch 'jc/apply-beyond-symlink'

"git apply" was not very careful about reading from, removing,
updating and creating paths outside the working tree (under
--index/--cached) or the current directory (when used as a
replacement for GNU patch).

* jc/apply-beyond-symlink:
apply: do not touch a file beyond a symbolic link
apply: do not read from beyond a symbolic link
apply: do not read from the filesystem under --index
apply: reject input that touches outside the working area

diff --cc builtin/apply.c
Simple merge

diff --cc t/t4122-apply-symlink-inside.sh
Simple merge