Add documentation for the repository section (modelcontextprotocol#174)

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## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->

Resolve modelcontextprotocol#173

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->

Copilot fixed my spelling mistakes.

## Breaking Changes
<!-- Will users need to update their code or configurations? -->

None.

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [x] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

Ideally the `id` would be populated by the publisher CLI tool "on the
way out" and MCP Registry would validate the `id`, perhaps using the
token used for auth in the case of private repositories.

Author: joelverhagen

docs/server-json/repository_references.md

@@ -0,0 +1,34 @@
+# Repository References in server.json
+
+The [`server.json` schema](schema.json) MAY contain a `repository` property at the root of the JSON object. The `repository` object provides metadata about the MCP server's source code. This enables users and security experts to inspect the code of the MCP service, thereby improving the transparency of what the MCP server is doing at runtime.
+
+The inclusion of the `repository` object is RECOMMENDED for both local and remote MCP servers.
+
+Consumers of the `server.json` metadata MAY use the `source` property to determine which specific source forge is used for hosting the MCP server's code. The value of `source` SHOULD be a string enum (a well-known list of values defined by the MCP Registry deployment).
+
+The `url` property MAY be used to browse the source code. Some source forges, such as GitHub, support `git clone <url>` on the URL, which also works for web browsing. For the purposes of the Official MCP Registry, the URL MUST be accessible in a web browser.
+
+The `id` property is owned and determined by the source forge, such as GitHub. This value SHOULD be stable across repository renames and, if applicable on the source forge, MAY be used to detect repository resurrection attacks. If a repository is renamed, the `id` value SHOULD remain constant. If the repository is deleted and then recreated later, the `id` value SHOULD change.
+
+Determining the `id` is specific to the source forge. For GitHub, the following [GitHub CLI](https://cli.github.com/) command MAY be used (works for both public and private repositories):
+
+```bash
+gh auth login
+gh api repos/<repo owner>/<repo name> --jq '.id'
+```
+
+MCP server registries MAY define their own policies for allowed `source` values and whether the `url` MUST be publicly accessible.
+
+An MCP server registry SHOULD validate that the `id` matches the given `url`, perhaps by invoking source-specific REST APIs to match the `id`. MCP server publish tooling MAY compute the `id` value dynamically and enrich the `server.json` payload provided to the publish endpoint to simplify the workflow.
+
+## Official MCP Registry Policies
+
+The `repository` metadata MAY be included in the `server.json`, as in the general MCP Registry protocol.
+
+The Official MCP Registry has policies related to the `repository` object that are stricter than those the general MCP Registry protocol allows.
+
+See the [`registry-schema.json`](registry-schema.json) for the allowed `source` values.
+
+The repository referenced by the `repository` property SHOULD be publicly accessible, but this is not REQUIRED.
+
+The `id` MUST match the repository referenced by the `url`.