Feature Request: "add" command for adding extra sites

Terms

• I have read the guidelines for Contributing to Roots Projects
• This request is not a duplicate of an existing issue
• This is not a personal support request that should be posted on the Roots Discourse community

Summary

Add trellis add command. This is usefull for adding new sites to an existing trellis project.

The existing trellis new command adds a complete new trellis project. It fills in a pre-configured setup. I would like to have a command that does the same but only for adding a new site to the project.

This way you dont have to copy-paste-edit the existing site. It's faster and foolproof.

Motivation

Why are we doing this?

To make it easier and foolproof to add a new sites to an existing trellis project.

What use cases does it support?

Users wanting to add more than one site to a trellis project.

What is the expected outcome?

A clean and pre-configured site setup added to the trellis project.

Potential conflicts / foreseeable issues

Check if there is a site with the same name already existing in the trellis project.

Additional Context

No response

Start by examining the existing trellis new command and how it creates a complete project. Define the corresponding site-only setup, including detection of an existing site with the same name; done means trellis add creates a clean, pre-configured site in an existing project without copying files manually.