I get "Option 'version' is unknown" if it comes after other user-defined options on the command line

Since version is pretty much built-in, it should never be “unknown”, especially if this message is immediately followed by helptext that clearly shows that it is a valid option.

3676 ~/fork/foo-etl$ dotnet etl/bin/Debug/netcoreapp3.0/etl.dll -c foo -d bar --version
etl 0.0.1
Copyright (C) 2020 etl

ERROR(S):
  Option 'version' is unknown.

  -c, --configdir     Required. Path to dir that contains client configurations

  -d, --invoicedir    Required. Path to dir that contains invoices are

  --help              Display this help screen.

  --version           Display version information.

[gbirchmeier]

I’ve just read the GNU standard regarding command-line params.

I now agree with you that (2) is the best option: params --help and --version should cause all other params to be ignored.

Since --help’s output includes the version, --version can be ignored if both are present.

[rmunn]

This is fixed by #686, which allow --help and --version to appear anywhere on the command line rather than only being handled in first position.