This commit adds a function which can be used to ensure all contents of
a directory can be accessed.
This function doesn't follow symlinks to check if they're pointing to
files which exist. Such symlinks can be useful later.
Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Upstream-commit: 1dedcd0d376f57abae5cadd38116c1aca2821330
Component: engine