Confusing error message suggests unsupported --kubeconfig flag

[ronak-701685]

What happened?

When running crossplane-diff without explicitly setting a kubeconfig, the tool fails with an error message that references unsupported flags:

W0926 ... Neither --kubeconfig nor --master was specified...
...
crossplane-diff: error: invalid configuration: no configuration has been provided

This is misleading, because crossplane-diff does not support the --kubeconfig flag. Attempting to use it results in:

crossplane-diff: error: unknown flag: --kubeconfig

How can we reproduce it?

1. Run crossplane-diff diff without setting the KUBECONFIG environment variable and without having a default kubeconfig at ~/.kube/config.

   unset KUBECONFIG
   crossplane-diff diff

2. Observe the following misleading error message:

   Neither --kubeconfig nor --master was specified...
   crossplane-diff: error: invalid configuration: no configuration has been provided
   

3. Attempting to use the --kubeconfig flag as suggested:

   crossplane-diff diff --kubeconfig /path/to/config

   Results in:

   crossplane-diff: error: unknown flag: --kubeconfig
   

4. Correct behavior is only achieved by setting the KUBECONFIG environment variable:

   export KUBECONFIG=/path/to/config
   crossplane-diff diff

This reproduces the misleading messaging and the lack of support for the --kubeconfig flag.

What environment did it happen in?

Crossplane version: v2.0