Function cachedir::mkdir_atomic

pub fn mkdir_atomic<P: AsRef<Path>>(directory: P) -> Result<bool>

Tries to create directory with a CACHEDIR.TAG file atomically and returns true if it created it or false if the directory already exists, regardless of if the CACHEDIR.TAG file exists in it or if it has the correct header.

This function first creates a temporary directory in the same directory where directory is supposed to exist. The temporary directory has a semi-random name based on the directory base name. Then the CACHEDIR.TAG file is created in the temporary directory and the temporary directory is attempted to be renamed to directory. This (as opposed to creating the directory with the final name and creating CACHEDIR.TAG file in it) is a way to ensure that the directory is always created with the CACHEDIR.TAG file. If we simply created the directory with the final name the program could be interrupted before CACHEDIR.TAG creation and the directory would remain not excluded from backups as this function does not attempt to verify or change the CACHEDIR.TAG file in directory if it already exists.