CopyDfPattern is to copy DFPattern's content.

MatchDfPattern returns true if location matches DFPattern, otherwise returns false.

UpdateDFPattern is to update DFPattern from the giving string(CommandParam.DownRule).

CommandLine stores all the command line parameters.

DFPattern is the url patterns.

HomeDir is the user home.

RegDomain is the domain of images registry.

RegProto is the protocol(HTTP/HTTPS) of images registry.

UseHTTPS indicates whether to use HTTPS protocol.

CommandParam is a struct that stores all the command line parameters.