fix: reuse existing license if user didn't set any

[suzaku]

GitHub now supports creating files like LICENSE for newly created repos.
Running cobra-cli init after cloning a newly created repo will now
empty that existing license.

[CLAassistant]

All committers have signed the CLA.

[nirs]

This is nicer, but the rest of the code use the previous style so this create inconsistency.

It would be better to keep the current style for this change, and if changing the way paths are created is needed, do this in the entire file or project.

[nirs]

Using exiting license makes sense, but this check ignores errors from os.Stat(), (other then fs.ErrNotExits). If the file exits and os.Stat failed, something is very wrong and failing is the best option.

But I think there is a better way - do we really want to overwrite existing license file if the user specify the license type? This does not feel like a careful way to modify user source tree.

So we can ensure that we never overwrite existing license, and handle the special case when the user did not specify the license, in which we will reuse the existing license.

Something like:

licenseFile, err := os.OpenFile(licensePath, O_CREATE|O_EXCL, 0755)
if err != nil {
    if errors.Is(err, fs.ErrExist) && p.Legal.Name == "None" {
        // User did not specify the license - use the existing one.
        return nil
    }
    return err
}