Imports of txtar-addmod command

PathSynopsis
bytesPackage bytes implements functions for the manipulation of byte slices.
flagPackage flag implements command-line flag parsing.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
golang.org/x/mod/modulePackage module defines the module.Version type along with support code.
golang.org/x/tools/txtarPackage txtar implements a trivial text-based file archive format.
logPackage log implements a simple logging package.
osPackage os provides a platform-independent interface to operating system functionality.
os/execPackage exec runs external commands.
path/filepathPackage filepath implements utility routines for manipulating filename paths in a way compatible with the target operating system-defined file paths.
stringsPackage strings implements simple functions to manipulate UTF-8 encoded strings.