fix(repos): return typed projected commit lists

Use an optional-field commit DTO for full and projected modern outputs while retaining exact legacy text. Cover SHA and nested commit projections, empty lists, and output schema conformance.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: SamMorrowDrums

pkg/github/repositories.go

@@ -155,6 +155,41 @@ type ListCommitsInput struct {
 	PerPage *int     `json:"perPage,omitempty"`
 }
 
+type ListCommitOutput struct {
+	SHA       *string            `json:"sha,omitempty"`
+	HTMLURL   *string            `json:"html_url,omitempty"`
+	Commit    *MinimalCommitInfo `json:"commit,omitempty"`
+	Author    *MinimalUser       `json:"author,omitempty"`
+	Committer *MinimalUser       `json:"committer,omitempty"`
+}
+
+func structuredListCommitsOutput(commits []MinimalCommit, fields []string) []ListCommitOutput {
+	output := make([]ListCommitOutput, 0, len(commits))
+	selected := func(field string) bool {
+		return len(fields) == 0 || slices.Contains(fields, field)
+	}
+	for _, commit := range commits {
+		item := ListCommitOutput{}
+		if selected("sha") {
+			item.SHA = new(commit.SHA)
+		}
+		if selected("html_url") {
+			item.HTMLURL = new(commit.HTMLURL)
+		}
+		if selected("commit") {
+			item.Commit = commit.Commit
+		}
+		if selected("author") {
+			item.Author = commit.Author
+		}
+		if selected("committer") {
+			item.Committer = commit.Committer
+		}
+		output = append(output, item)
+	}
+	return output
+}
+
 func ListCommits(t translations.TranslationHelperFunc) inventory.ServerTool {
 	schema := &jsonschema.Schema{
 		Type: "object",
@@ -196,7 +231,7 @@ func ListCommits(t translations.TranslationHelperFunc) inventory.ServerTool {
 	)
 	WithPagination(schema)
 
-	return NewTool[ListCommitsInput, []MinimalCommit](
+	return NewTool[ListCommitsInput, []ListCommitOutput](
 		ToolsetMetadataRepos,
 		mcp.Tool{
 			Name:        "list_commits",
@@ -208,7 +243,7 @@ func ListCommits(t translations.TranslationHelperFunc) inventory.ServerTool {
 			InputSchema: schema,
 		},
 		scopes.PublicRead(scopes.Repo),
-		func(ctx context.Context, deps ToolDependencies, _ *mcp.CallToolRequest, input ListCommitsInput) (*mcp.CallToolResult, []MinimalCommit, error) {
+		func(ctx context.Context, deps ToolDependencies, _ *mcp.CallToolRequest, input ListCommitsInput) (*mcp.CallToolResult, []ListCommitOutput, error) {
 			if input.Owner == "" {
 				return utils.NewToolResultError("missing required parameter: owner"), nil, nil
 			}
@@ -302,10 +337,7 @@ func ListCommits(t translations.TranslationHelperFunc) inventory.ServerTool {
 			// follows the same public-untrusted / private-trusted rule as file
 			// contents. Confidentiality follows repo visibility.
 			result = attachRepoVisibilityIFCLabel(ctx, deps, client, input.Owner, input.Repo, result, ifc.LabelCommitContents)
-			if len(input.Fields) > 0 {
-				return result, nil, nil
-			}
-			return result, minimalCommits, nil
+			return result, structuredListCommitsOutput(minimalCommits, input.Fields), nil
 		},
 		normalizeTypedReadArguments(nil, false),
 	)

pkg/github/typed_repository_commit_outputs_test.go

@@ -89,6 +89,10 @@ func TestTypedRepositoryCommitOutputs(t *testing.T) {
 		GetReposCommitsByOwnerByRepo: func(w http.ResponseWriter, r *http.Request) {
 			assert.Equal(t, "4", r.URL.Query().Get("page"))
 			assert.Equal(t, "9", r.URL.Query().Get("per_page"))
+			if r.URL.Query().Get("sha") == "empty" {
+				mockResponse(t, http.StatusOK, []*github.RepositoryCommit{})(w, r)
+				return
+			}
 			mockResponse(t, http.StatusOK, []*github.RepositoryCommit{commit})(w, r)
 		},
 	}
@@ -137,6 +141,26 @@ func TestTypedRepositoryCommitOutputs(t *testing.T) {
 					args: map[string]any{"owner": "owner", "repo": "repo", "page": "4", "perPage": "9"},
 					text: expectedList,
 				},
+				{
+					name: "list_commits",
+					args: map[string]any{"owner": "owner", "repo": "repo", "page": "4", "perPage": "9", "fields": []any{"sha"}},
+					text: `[{"sha":"abc123"}]`,
+				},
+				{
+					name: "list_commits",
+					args: map[string]any{"owner": "owner", "repo": "repo", "page": "4", "perPage": "9", "fields": []any{"commit"}},
+					text: `[{"commit":{"message":"A commit"}}]`,
+				},
+				{
+					name: "list_commits",
+					args: map[string]any{"owner": "owner", "repo": "repo", "page": "4", "perPage": "9", "sha": "empty"},
+					text: `[]`,
+				},
+				{
+					name: "list_commits",
+					args: map[string]any{"owner": "owner", "repo": "repo", "page": "4", "perPage": "9", "sha": "empty", "fields": []any{"sha", "commit"}},
+					text: `[]`,
+				},
 			}
 			for _, call := range calls {
 				result, err := session.CallTool(context.Background(), &mcp.CallToolParams{Name: call.name, Arguments: call.args})
@@ -172,7 +196,12 @@ func TestTypedRepositoryCommitOutputs(t *testing.T) {
 			require.NoError(t, err)
 			require.False(t, filtered.IsError, filtered)
 			assert.Equal(t, `[{"sha":"abc123"}]`, getTextResult(t, filtered).Text)
-			assert.Nil(t, filtered.StructuredContent, "field projection keeps the legacy wire shape")
+			if protocolVersion == "2025-11-25" {
+				assert.Nil(t, filtered.StructuredContent)
+			} else {
+				require.NotNil(t, filtered.StructuredContent)
+				assert.JSONEq(t, `[{"sha":"abc123"}]`, mustMarshalJSON(t, filtered.StructuredContent))
+			}
 		})
 	}
 }