Determines how symlinks are followed.
Materialize all symlinks, whether they are internal or external to the source directory.
Forbids source from having any symlinks pointing outside of the source tree.
This is the safest mode of operation as it ensures that copy operations
won’t materialize files from the user’s file system. Internal symlinks are
If the copy operation runs into an external symlink, it will fail.
Only follows symlinks that are external to the source directory.
Never follow symlinks.