Add support for org-level discussions in list_discussion_categories tool

[tommaso-moro]

Overview

Closes: #818

This PR improves the existing list_discussion_categories tool, by adding logic to handle organisation-level discussions. (It implements similar logic to what I implemented in PR #775 )

Changes introduced

Before, the "repo" argument was required, so when the user would ask to query org-level discussions the model would either (i) hallucinate random values for repo or (ii) it would have to know the implementation detail about the Github API which is that org-level discussions are stored in a hidden .github repo.
With these changes:

• the repo argument is made optional
• the tool description is updated so that the model knows to omit repo if discussions are to be queried at the org-level
• the repo value is deterministically set to .github when needed
• the tests are updated to reflect these changes

Before (the model hallucinates repo values)

After (the model correctly omits the repo argument, and the tool uses the deterministic flow to query org-level discussions)

[mattdholloway]

lgtm

[Copilot]

Pull Request Overview

This PR enhances the list_discussion_categories tool to support organization-level discussions by making the repo parameter optional and automatically defaulting to .github when querying at the organization level.

• Makes the repo parameter optional instead of required
• Adds logic to default to .github repo when repo is not provided for organization-level queries
• Updates tool description and documentation to clarify the new behavior

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pkg/github/discussions.go	Makes repo parameter optional and adds logic to default to .github for org-level queries
pkg/github/discussions_test.go	Adds comprehensive test coverage for both repository and organization-level scenarios
README.md	Updates documentation to reflect the optional repo parameter

Comments suppressed due to low confidence (2)

pkg/github/discussions_test.go:648

• The test verifies that only 'owner' is required but doesn't verify that 'repo' is not in the required array. Consider adding an explicit assertion that 'repo' is not required to make the test more complete.

	mockClient := githubv4.NewClient(nil)
	toolDef, _ := ListDiscussionCategories(stubGetGQLClientFn(mockClient), translations.NullTranslationHelper)
	assert.Equal(t, "list_discussion_categories", toolDef.Name)
	assert.NotEmpty(t, toolDef.Description)
	assert.Contains(t, toolDef.Description, "or organisation")
	assert.Contains(t, toolDef.InputSchema.Properties, "owner")
	assert.Contains(t, toolDef.InputSchema.Properties, "repo")
	assert.ElementsMatch(t, toolDef.InputSchema.Required, []string{"owner"})

pkg/github/discussions_test.go:733

• Consider adding a test case where repo is explicitly set to an empty string to verify the behavior when the parameter is present but empty, as this might behave differently from when the parameter is completely omitted.

			name: "list org-level discussion categories (no repo provided)",
			reqParams: map[string]interface{}{
				"owner": "owner",
				// repo is not provided, it will default to ".github"
			},

[mattdholloway]

Test improvements look great 🚀