feat: list_discussions sort by updatedAt & createdAt, return updatedAt and author

[tommaso-moro]

Addresses #670

Overview
This PR expands the functionality of the list_discussions tool. It adds

• The updatedAt and author.login (i.e. username) fields to the discussions payload in the list_discussions tool
• The ability to order discussions by field (updated_at and created_at) and direction (ascending order, descending order)

Refactoring
The PR includes extensive refactoring of the list_discussions tool to handle optional parameters in our graphql queries. This was needed because the githubv4 library requires GraphQL queries to be defined using Go struct tags that must be known at compile time, so we could not dynamically construct query strings at runtime based on user input.

The changes made include

• Introduced reusable DiscussionFragment struct to avoid field duplication
• Created 4 pre-defined query variants:
  • BasicNoOrder: No optional parameters (uses GitHub API's defaults)
  • BasicWithOrder: Only ordering parameters
  • WithCategoryNoOrder: Only category filtering
  • WithCategoryAndOrder: Both category and ordering
• Added runtime query selection logic to choose the appropriate variant based on user input

Tests
I updated the tests in discussions_test.go to match the new queries, and to test the new ordering functionality with different sorting combinations.

Demo

Simple "list discussions" prompt

Ordering: from most recently created to least recently created

Ordering: from least recently updated to most recently updated

Less explicit prompt: show me discussions from last 10 days

Ordering with weaker model (GPT-4o)

---

Note: this PR adds author data to the payload of the list_discussions tool but doesn't add support for filtering by author when listing discussions because that is not supported on the discussions field in the API, and it would need to be achieved in a separate search tool.

[Copilot]

Pull Request Overview

This PR enhances the list_discussions tool by adding ordering capabilities and expanding the discussion payload to include author information and updated timestamps. The changes enable users to sort discussions by creation or update date in ascending or descending order, while maintaining backward compatibility with existing functionality.

• Added updatedAt and author.login fields to the discussion payload
• Implemented ordering support with orderBy and direction parameters
• Refactored GraphQL query handling to support optional parameters through pre-defined query variants

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 10 comments.

File	Description
pkg/github/discussions.go	Added new query struct types, ordering logic, and GraphQL query selection based on parameters
pkg/github/discussions_test.go	Updated test data and added comprehensive test cases for ordering functionality
README.md	Updated documentation to reflect new ordering parameters

[LuluBeatson]

Thanks @tommaso-moro for taking on this issue and refactoring the ListDiscussion GraphQL queries.

I have merged main into this branch, bringing GraphQL pagination to Discussion tools.

Plain List

list the last 20 discussions in facebook/react

List with Pagination

list all discussions in facebook/react with page size 3
...
Yes fetch the next page too

List with Pagination & Reverse CreatedAt Sorting

list all discussions in facebook/react with page size 3 in reverse order of creation

List with Pagination & UpdatedAt Sorting

list all discussions in facebook/react with page size 3 in order of last update

[mattdholloway]

This looks great! The only potential issue I can see is with the following user flow:

1. Gets page 1 with a given sort order eg. ordered by time created
2. Uses endCursor from that response
3. Makes another request with a new sort order

A potential improvement might be to force the pagination to be restarted when the sort order is changed so that the results are consistent. Perhaps updating the tool description for endCursor with a warning to the effect of 'this becomes invalid if the sort order changes' might help?