feat: Gitlab list repository tree tool

[BobMerkus]

This PR adds a list_repository_tree tool for the Gitlab MCP, so AI agents can explore repositories interactively.

Description

This PR adds a list_repository_tree tool for the Gitlab MCP, so It can explore a repository interactively. It wraps around the corresponding List repository tree.

Server Details

• Server: gitlab
• Changes to: tools

Motivation and Context

The AI agents are in the dark regarding the structure of a repository and can only read specific files in their entirety. This PR adds the list_repository_tree to allow the AI to explore the repository before reading/updating specific files.

How Has This Been Tested?

Yes, have tested locally using Claude Sonnet 3.7

Breaking Changes

No

Types of changes

• 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)
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follows MCP security best practices
• I have updated the server's README accordingly
• I have tested this with an LLM client
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have documented all environment variables and configuration options

Additional context

See List repository tree - Gitlab Documentation.

Get a list of repository files and directories in a project. This endpoint can be accessed without authentication if the repository is publicly accessible.

This command provides essentially the same features as the git ls-tree command. For more information, refer to the section Tree Objects in the Git internals documentation.

Attribute	Type	Required	Description
id	integer or string	yes	The ID or URL-encoded path of the project.
page_token	string	no	The tree record ID at which to fetch the next page. Used only with keyset pagination.
pagination	string	no	If keyset, use the keyset-based pagination method.
path	string	no	The path inside the repository. Used to get content of subdirectories.
per_page	integer	no	Number of results to show per page. If not specified, defaults to 20. For more information, see Pagination.
recursive	boolean	no	Boolean value used to get a recursive tree. Default is false.
ref	string	no	The name of a repository branch or tag or, if not given, the default branch.