[BUG] positional argument cran_packages ignored when --package-indexes argument given to grayskull cran

[matthewfeickert]

Describe the bug
For grayskull v2.9.1, if you try to generate a recipe for an R package using grayskull cran and pass the optional --package-indexes argument the required positional argument cran_packages is ignored.

To Reproduce
Steps to reproduce the behavior:

$ docker run --rm -ti ghcr.io/prefix-dev/pixi:latest 
root@dd24e7a37c8f:/# pixi global install grayskull
Global environments as specified in '/root/.pixi/manifests/pixi-global.toml'
└── grayskull: 2.9.1 (installed)
    └─ exposes: grayskull, greyskull, conda-grayskull, conda-greyskull
root@dd24e7a37c8f:/# grayskull cran --help
usage: grayskull cran [-h] [--stdout STDOUT] [--list-missing-deps] [--package-indexes PACKAGE_INDEXES [PACKAGE_INDEXES ...]] [--download] [--maintainers MAINTAINERS [MAINTAINERS ...]] [--output OUTPUT]
                      [--strict-conda-forge] [--sections {package,source,build,requirements,test,about,extra} [{package,source,build,requirements,test,about,extra} ...]] [--use-v1-format]
                      cran_packages [cran_packages ...]

positional arguments:
  cran_packages         Specify the CRAN packages name.

options:
  -h, --help            show this help message and exit
  --stdout STDOUT       Disable or enable stdout, if it is False, Grayskull will disable the prints. Default is True
  --list-missing-deps   After the execution Grayskull will print all the missing dependencies.
  --package-indexes PACKAGE_INDEXES [PACKAGE_INDEXES ...]
                        List of package indexes to check for existing packages. Can be channel names (e.g., conda-forge) or full URLs (e.g., https://internal-conda.example.com). For custom API
                        structures, use the {pkg_name} placeholder (e.g., https://internal-conda.example.com/api/{pkg_name}/available). Default is conda-forge.",
  --download, -d        Download the sdist package and PyPI information in the same folder the recipe is located.
  --maintainers MAINTAINERS [MAINTAINERS ...], -m MAINTAINERS [MAINTAINERS ...]
                        List of maintainers which will be added to the recipe.
  --output OUTPUT, -o OUTPUT
                        Path to where the recipe will be created
  --strict-conda-forge  It will generate the recipes strict for the conda-forge channel.
  --sections {package,source,build,requirements,test,about,extra} [{package,source,build,requirements,test,about,extra} ...], -s {package,source,build,requirements,test,about,extra} [{package,source,build,requirements,test,about,extra} ...]
                        If sections are specified, grayskull will populate just the sections informed.
  --use-v1-format, -u   Returns a recipe file in the V1 format, used by rattler-build. NOTE: This is experimental.
root@dd24e7a37c8f:/# grayskull cran --package-indexes https://carpentries.r-universe.dev/api/packages/{pkg_name}/ varnish
usage: grayskull cran [-h] [--stdout STDOUT] [--list-missing-deps] [--package-indexes PACKAGE_INDEXES [PACKAGE_INDEXES ...]] [--download] [--maintainers MAINTAINERS [MAINTAINERS ...]] [--output OUTPUT]
                      [--strict-conda-forge] [--sections {package,source,build,requirements,test,about,extra} [{package,source,build,requirements,test,about,extra} ...]] [--use-v1-format]
                      cran_packages [cran_packages ...]
grayskull cran: error: the following arguments are required: cran_packages
root@dd24e7a37c8f:/# grayskull cran --package-indexes conda-forge tinkr
usage: grayskull cran [-h] [--stdout STDOUT] [--list-missing-deps] [--package-indexes PACKAGE_INDEXES [PACKAGE_INDEXES ...]] [--download] [--maintainers MAINTAINERS [MAINTAINERS ...]] [--output OUTPUT]
                      [--strict-conda-forge] [--sections {package,source,build,requirements,test,about,extra} [{package,source,build,requirements,test,about,extra} ...]] [--use-v1-format]
                      cran_packages [cran_packages ...]
grayskull cran: error: the following arguments are required: cran_packages

Expected behavior

Run successfully, checking for the package on another package index other than CRAN.

Outputs
If applicable, add the output to help explain your problem.

Environment:

root@dd24e7a37c8f:/# pixi global list
Global environments as specified in '/root/.pixi/manifests/pixi-global.toml'
└── grayskull: 2.9.1 
    └─ exposes: grayskull, greyskull, conda-grayskull, conda-greyskull
root@dd24e7a37c8f:/# grayskull --version
2.9.1

Additional context
Add any other context about the problem here.

Similar to Issue #532, it would be very useful to be able to target GitHub as well.

[matthewfeickert]

Related to and motivated by bgruening/conda_r_skeleton_helper#68.