Completion support for PowerShell.
Fixes#729
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Requires PS 5.0+ for the `Microsoft.PowerShell.Core\Register-ArgumentCompleter` commandlet. Earlier versions using the equivalent commandlet from TabExpansionPlusPlus may work, but I haven't tested that. PS 5.0 is available for Windows 7 and non-Windows anyway.
The resulting script can be used by pasting it into the PS profile or saving it to a file and sourcing it into the PS profile in the usual way.
Now one can build CLIs that support things like `mv <files>... <target>`
There are a few requirements and caveats;
* The final positional argument (and all positional arguments prior) *must* be required
* Only one positional argument may be `multiple(true)`
* Only the second to last, or last positional argument may be `multiple(true)`
Closes#725
Prior to this commit, conflicting error messages and the suggeseted usage would depend on whether
you defined the conflict on both arguments, or just one, and the order in which you specified the
conflicting arguments at runtime.
Now they are symetrical, meaning the suggestions from the error message are consistent, and it no
longer matters if you specify the conflict in one, or both arguments.
Closes#718
Derive display order after propagation
Don't attempt to change the display order of flags/options until any app settings have been propagated down from a parent `App` in case `DeriveDisplayOrder` and/or `UnifiedHelpMessage` are propagated.
Adds tests that try to stress the combinations of `DeriveDisplayOrder` and `UnifiedHelpMessage` along with propagating them to subcommands and explicitly setting a display order.
Don't attempt to change the display order of flags/options until any app
settings have been propagated down from a parent App in case DeriveDisplayOrder
and/or UnifiedHelpMessage are propagated.
Fixes#706
Try and stress the combinations of DeriveDisplayOrder and UnifiedHelpMessage
along with propagating them to subcommands and explicitly setting a display
order.
The new tests
derive_order_subcommand_propagate
unified_help_and_derive_order_subcommand_propagate
unified_help_and_derive_order_subcommand_propagate_with_explicit_display_order
are currently failing because of bug #706.
