First, ack looks for a global ackrc.
Then, ack looks for a user-specific ackrc if the HOME environment variable is set. This is either `$HOME/.ackrc` or `$HOME/_ackrc`.
Then, ack looks for a project-specific ackrc file. ack searches up the directory hierarchy for the first `.ackrc` or `_ackrc` file. If this is one of the ackrc files found in the previous steps, it is not loaded again.
It is a fatal error if a directory contains both `.ackrc` and `_ackrc`.
After ack loads the options from the found ackrc files, ack looks at the ACKRC_OPTIONS environment variable.
Finally, ack takes settings from the command line.
Creates a new config finder.
Locates config files, and returns a list of them.
Reads the contents of the .ackrc file and returns the arguments.