Docs
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- Username handling

    Change default semantics to pick up $USER from the environment and not prompt for it.
    Add switch to force username prompting  (-N)
    When prompting for username, show $USER as default if present.

- Commenting now supported both on -H and in host list files - freeform/block comments

- File Xfer (-G, -P)

   Destination is always a *directory*
   No ~/ interpolation
   Transfers happen before command execution
   Any tranfer error on any host aborts program
   If there's nothing to do, program silently ends
   Gets done before Puts
   Gets prepend hostname to saved file