Allo to execute user-defined commands if strategy exists in $ORIGIN_DIR/.deliver/strategies/
Display help for user-defined commands if additional help exists.

This help is printed in addition to the default help
if the "print_custom_commands_help" function exists
in the user defined help script $ORIGIN_DIR/.deliver/help
Check whether user-defined commands accept arguments.

If the "accepts_custom_command_argument" function exists
in the user defined help script $ORIGIN_DIR/.deliver/help
a warning about unused arguments is printed only, if that
function returns 1
Use revision of tag when building tag.