Syntax: rename old-alias-name new-alias-name

    The rename command is used to rename an alias without altering
    its expansion value:

    db> add postmaster "system@thor.example.com"
    [Entry added to database]
    db> show postmaster
    Key         Value
    ----------  -----------------------------
    postmaster  system@thor.example.com
    [1 entry shown]
    db> rename postmaster post
    [1 entry renamed]
    db> show post
    Key         Value
    ----------  -----------------------------
    post        system@thor.example.com
    [1 entry shown]
    db>