A Command is an implementation of a go command like go build or go fix.

CoverVar holds the name of the generated coverage variables targeting the named file.

A Generator represents the state of a single Go source file being scanned for generator commands.

A Package describes a single package found in a directory.

A PackageError describes an error loading information about a package.

TrackingWriter tracks the last byte written on every write so we can avoid printing a newline if one was already written or if there is no output at all.