Resolves #925
Resolves #3134

Before the change?

• When creating a repository from a template with visibility = "internal", the repository was created as public due to incorrect handling of the Private boolean field
• The code only set Private=true when visibility == "private", causing visibility = "internal" to default to Private=false (public)
• This resulted in repositories being temporarily exposed publicly before being updated to internal visibility
• Security Impact: Repositories intended to be internal to an organization were briefly accessible to the public, potentially exposing sensitive data

After the change?

• Modified the isPrivate logic to set Private=true for both "private" and "internal" visibility values
• Repositories with visibility = "internal" are now correctly created as private initially
• The visibility is then properly updated to "internal" via the existing PATCH request in resourceGithubRepositoryUpdate()
• Security Fixed: No public exposure window - repositories remain private/internal throughout the entire creation process
• Added inline comment explaining the API limitation and two-step process

Pull request checklist

• Schema migrations have been created if needed (example)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Note on checklist items:

• Schema migrations: Not needed - no schema changes required
• Tests: Added new test case "sets internal visibility for repositories created by a template" that verifies repositories created from templates with visibility = "internal" are correctly created as internal
• Docs: No documentation updates needed - this is a bug fix that makes the existing documented behavior work correctly

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

This is a bug fix that corrects the existing behavior to match the documented and expected functionality. Users who specify visibility = "internal" for template-based repositories will now get the correct behavior without any changes to their Terraform configurations.

Technical Details

Root Cause: The GitHub template creation API (POST /repos/{template_owner}/{template_repo}/generate) only accepts a private boolean parameter and does not support the visibility parameter directly.

Code Change (line ~660 in github/resource_github_repository.go):

// Before:
isPrivate := repoReq.GetVisibility() == "private"

// After:
// Template API only supports Private boolean, so treat "internal" as private, then update via PATCH.
isPrivate := repoReq.GetVisibility() == "private" || repoReq.GetVisibility() == "internal"