GitLab

The writable branch prepares a few files and dirs for whiteouts.
For branch filesystems which doesn't support link(2), there is "nolwh"
attribute. On the branch which is specified this attribute, aufs never
try link(2) for whitout and always creat(2) it.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>