Plugin Marketplace clone does not pull submodules

[brandonh-msft]

Describe the bug

When adding a custom Marketplace, the clone of the target marketplace repo does not clone subrepositories. This means that the marketplace cannot utilize submodules as "pointers" to plugins in other repos, which prevents a "curated" marketplace capability.

Affected version

1.0.6-1

Steps to reproduce the behavior

1. Create a marketplace with a submodule that points to a plugin. For example, add the awesome-copilot repo as a submodule to the marketplace,
2. In the marketplace manifest, point to a skill within a plugin of the subrepo - for example ./curated/awesome-copilot/plugins/csharp-dotnet-development/skills/dotnet-best-practices
3. Add the marketplace into GHCP - this will work w/o issue, and show the plugin you created to point at the awesome-copilot skill without issue
4. Add the plugin you created to GHCP - this will also work without issue but the skill will not activate in GHCP

Expected behavior

Everything defined in any submodules (recursively) in a marketplace is available to GHCP

Additional context

No response

[vslatten]

Supported. Would be great to have the ability for an organization to have a curated marketplace, yet let the plugins themselves live in any repo whose changes they should reflect. Example: A repository with documentation about an internal platform. If you change how the documentation is structured, you may want to change the corresponding plugin (e.g. MCP server serving docs) in the same PR.