@@ -17,13 +17,13 @@ type Service interface {
	Count(ctx context.Context, repo string, opt ListOptions) (uint64, error)

	// Get a change.
	Get(ctx context.Context, repo string, id uint64) (Change, error)
	// ListCommits lists change commits.
	ListCommits(ctx context.Context, repo string, id uint64) ([]Commit, error)
	ListCommits(ctx context.Context, repo string, id uint64, opt *ListCommitsOptions) ([]Commit, error)
	// Get a change diff.
	GetDiff(ctx context.Context, repo string, id uint64) ([]byte, error)
	GetDiff(ctx context.Context, repo string, id uint64, opt *ListCommitsOptions) ([]byte, error)

	// ListComments lists comments for specified change id.
	ListComments(ctx context.Context, repo string, id uint64, opt *ListCommentsOptions) ([]issues.Comment, error)
	// ListEvents lists events for specified change id.
	ListEvents(ctx context.Context, repo string, id uint64, opt *ListCommentsOptions) ([]issues.Event, error)
@@ -42,11 +42,11 @@ type Change struct {
	Commits int // Number of commits (not populated during list operation).
}

type Commit struct {
	SHA        string
	Message    string
	Message    string // TODO: Consider splitting into Subject, Body.
	Author     users.User
	AuthorTime time.Time
}

// State represents the change state.
@@ -72,10 +72,15 @@ type StateFilter State
const (
	// AllStates is a state filter that includes all issues.
	AllStates StateFilter = "all"
)

type ListCommitsOptions struct {
	// Commit is the commit ID of the commit to fetch.
	Commit string
}

// ListCommentsOptions controls pagination.
type ListCommentsOptions struct {
	// Start is the index of first result to retrieve, zero-indexed.
	Start int

@@ -123,15 +123,15 @@ func state(status string) changes.State {
	default:
		panic("unreachable")
	}
}

func (s service) ListCommits(ctx context.Context, _ string, id uint64) ([]changes.Commit, error) {
func (s service) ListCommits(ctx context.Context, _ string, id uint64, opt *changes.ListCommitsOptions) ([]changes.Commit, error) {
	return nil, fmt.Errorf("ListCommits: not implemented")
}

func (s service) GetDiff(ctx context.Context, _ string, id uint64) ([]byte, error) {
func (s service) GetDiff(ctx context.Context, _ string, id uint64, opt *changes.ListCommitsOptions) ([]byte, error) {
	diff, _, err := s.cl.Changes.GetPatch(fmt.Sprint(id), "current", &gerrit.PatchOptions{
		Path: "src", // TODO.
	})
	if err != nil {
		return nil, err

@@ -206,43 +206,66 @@ func (s service) Get(ctx context.Context, rs string, id uint64) (changes.Change,
		CreatedAt: pr.CreatedAt.Time,
		Commits:   pr.Commits.TotalCount,
	}, nil
}

func (s service) ListCommits(ctx context.Context, rs string, id uint64) ([]changes.Commit, error) {
func (s service) ListCommits(ctx context.Context, rs string, id uint64, opt *changes.ListCommitsOptions) ([]changes.Commit, error) {
	repo, err := ghRepoSpec(rs)
	if err != nil {
		// TODO: Map to 400 Bad Request HTTP error.
		return nil, err
	}
	cs, _, err := s.clV3.PullRequests.ListCommits(ctx, repo.Owner, repo.Repo, int(id), nil)
	if err != nil {
		return nil, err
	}
	var commits []changes.Commit
	for _, c := range cs {
		commits = append(commits, changes.Commit{
	switch opt {
	case nil:
		cs, _, err := s.clV3.PullRequests.ListCommits(ctx, repo.Owner, repo.Repo, int(id), nil)
		if err != nil {
			return nil, err
		}
		var commits []changes.Commit
		for _, c := range cs {
			commits = append(commits, changes.Commit{
				SHA:        *c.SHA,
				Message:    *c.Commit.Message,
				Author:     ghUser(c.Author),
				AuthorTime: *c.Commit.Author.Date,
			})
		}
		return commits, nil
	default:
		c, _, err := s.clV3.Repositories.GetCommit(ctx, repo.Owner, repo.Repo, opt.Commit)
		if err != nil {
			return nil, err
		}
		return []changes.Commit{{
			SHA:        *c.SHA,
			Message:    *c.Commit.Message,
			Author:     ghUser(c.Author),
			AuthorTime: *c.Commit.Author.Date,
		})
		}}, nil
	}
	return commits, nil
}

func (s service) GetDiff(ctx context.Context, rs string, id uint64) ([]byte, error) {
func (s service) GetDiff(ctx context.Context, rs string, id uint64, opt *changes.ListCommitsOptions) ([]byte, error) {
	repo, err := ghRepoSpec(rs)
	if err != nil {
		// TODO: Map to 400 Bad Request HTTP error.
		return nil, err
	}
	diff, _, err := s.clV3.PullRequests.GetRaw(ctx, repo.Owner, repo.Repo, int(id), github.RawOptions{Type: github.Diff})
	if err != nil {
		return nil, err
	switch opt {
	case nil:
		diff, _, err := s.clV3.PullRequests.GetRaw(ctx, repo.Owner, repo.Repo, int(id), github.RawOptions{Type: github.Diff})
		if err != nil {
			return nil, err
		}
		return []byte(diff), nil
	default:
		diff, _, err := s.clV3.Repositories.GetCommitRaw(ctx, repo.Owner, repo.Repo, opt.Commit, github.RawOptions{Type: github.Diff})
		if err != nil {
			return nil, err
		}
		return []byte(diff), nil
	}
	return []byte(diff), nil
}

func (s service) ListComments(ctx context.Context, rs string, id uint64, opt *changes.ListCommentsOptions) ([]issues.Comment, error) {
	// TODO: Respect opt.Start and opt.Length, if given.

@@ -104,15 +104,15 @@ func (s service) Count(_ context.Context, repo string, opt changes.ListOptions)
func (s service) Get(ctx context.Context, _ string, id uint64) (changes.Change, error) {
	// TODO.
	return changes.Change{}, fmt.Errorf("Get: not implemented")
}

func (s service) ListCommits(ctx context.Context, _ string, id uint64) ([]changes.Commit, error) {
func (s service) ListCommits(ctx context.Context, _ string, id uint64, opt *changes.ListCommitsOptions) ([]changes.Commit, error) {
	return nil, fmt.Errorf("ListCommits: not implemented")
}

func (s service) GetDiff(ctx context.Context, _ string, id uint64) ([]byte, error) {
func (s service) GetDiff(ctx context.Context, _ string, id uint64, opt *changes.ListCommitsOptions) ([]byte, error) {
	// TODO.
	return nil, fmt.Errorf("GetDiff: not implemented")
}

func state(status string) changes.State {