fix(vcs): thread CommitID through abstraction layer (#114)

Add CommitID field to vcs.ReviewRequest so the commit anchor propagates
through the vcs.Client interface to platform adapters.

Changes:
- vcs/types.go: Add CommitID string field to ReviewRequest
- gitea/client.go: Add commitID parameter to PostReview, include in API payload
- gitea/adapter.go: Pass req.CommitID to underlying client
- github/review.go: Use req.CommitID as primary, fall back to comment-level
- cmd/review-bot/main.go: Set CommitID on ReviewRequest from pr.Head.SHA

Fixes #114

gitea/adapter.go

@@ -170,9 +170,9 @@ func (a *Adapter) PostReview(ctx context.Context, owner, repo string, number int
 			if err != nil {
 				return nil, fmt.Errorf("translate position %d in %s: %w", c.Position, c.Path, err)
 			}
-			// CommitID from vcs.ReviewComment is intentionally not forwarded:
-			// Gitea review comments are pinned to the PR head SHA automatically,
-			// and the CreatePullReview API has no per-comment commit_id field.
+			// Per-comment CommitID is not forwarded to Gitea inline comments:
+			// Gitea's CreatePullReview API has no per-comment commit_id field.
+			// The review-level commit anchor is set via req.CommitID instead.
 			giteaComments = append(giteaComments, ReviewComment{
 				Path:        c.Path,
 				NewPosition: int64(lineNum),
@@ -181,7 +181,7 @@ func (a *Adapter) PostReview(ctx context.Context, owner, repo string, number int
 		}
 	}
 
-	review, err := a.client.PostReview(ctx, owner, repo, number, event, req.Body, giteaComments)
+	review, err := a.client.PostReview(ctx, owner, repo, number, event, req.Body, req.CommitID, giteaComments)
 	if err != nil {
 		return nil, fmt.Errorf("post review: %w", err)
 	}

gitea/adapter_test.go

@@ -408,3 +408,73 @@ func TestAdapter_RequestReviewerSelf(t *testing.T) {
 		t.Fatalf("RequestReviewerSelf() error = %v", err)
 	}
 }
+
+func TestAdapter_PostReview_CommitID_Threading(t *testing.T) {
+	var gotPayload struct {
+		Body     string `json:"body"`
+		Event    string `json:"event"`
+		CommitID string `json:"commit_id"`
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewDecoder(r.Body).Decode(&gotPayload)
+		json.NewEncoder(w).Encode(map[string]any{
+			"id":        1,
+			"body":      "test",
+			"user":      map[string]any{"login": "bot"},
+			"commit_id": "abc123def456",
+		})
+	}))
+	defer server.Close()
+
+	client := gitea.NewClient(server.URL, "token")
+	adapter := gitea.NewAdapter(client)
+
+	review, err := adapter.PostReview(context.Background(), "owner", "repo", 1, vcs.ReviewRequest{
+		Body:     "LGTM",
+		Event:    vcs.ReviewEventApprove,
+		CommitID: "abc123def456",
+		// No comments → no diff fetch needed
+	})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if gotPayload.CommitID != "abc123def456" {
+		t.Errorf("commit_id = %q, want %q", gotPayload.CommitID, "abc123def456")
+	}
+	if review.CommitID != "abc123def456" {
+		t.Errorf("review.CommitID = %q, want %q", review.CommitID, "abc123def456")
+	}
+}
+
+func TestAdapter_PostReview_EmptyCommitID_Omitted(t *testing.T) {
+	var gotRawPayload map[string]any
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewDecoder(r.Body).Decode(&gotRawPayload)
+		json.NewEncoder(w).Encode(map[string]any{
+			"id":   1,
+			"body": "test",
+			"user": map[string]any{"login": "bot"},
+		})
+	}))
+	defer server.Close()
+
+	client := gitea.NewClient(server.URL, "token")
+	adapter := gitea.NewAdapter(client)
+
+	_, err := adapter.PostReview(context.Background(), "owner", "repo", 1, vcs.ReviewRequest{
+		Body:  "looks good",
+		Event: vcs.ReviewEventComment,
+		// CommitID intentionally empty
+	})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	// With empty CommitID and omitempty tag, the field should not appear in JSON
+	if _, exists := gotRawPayload["commit_id"]; exists {
+		t.Errorf("commit_id should be omitted when empty, but was present: %v", gotRawPayload["commit_id"])
+	}
+}

gitea/client.go

@@ -186,18 +186,22 @@ func (c *Client) GetFileContentRef(ctx context.Context, owner, repo, filepath, r
 }
 
 // PostReview submits a review to a PR and returns the created review.
-// event should be "APPROVED" or "REQUEST_CHANGES".
+// event should be one of "APPROVED", "REQUEST_CHANGES", or "COMMENT".
+// commitID anchors the review to a specific commit SHA. If empty, Gitea
+// defaults to the current PR head.
 // comments are optional inline comments attached to specific lines.
-func (c *Client) PostReview(ctx context.Context, owner, repo string, number int, event, body string, comments []ReviewComment) (*Review, error) {
+func (c *Client) PostReview(ctx context.Context, owner, repo string, number int, event, body, commitID string, comments []ReviewComment) (*Review, error) {
 	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number)
 
 	payload := struct {
 		Body     string          `json:"body"`
 		Event    string          `json:"event"`
+		CommitID string          `json:"commit_id,omitempty"`
 		Comments []ReviewComment `json:"comments,omitempty"`
 	}{
 		Body:     body,
 		Event:    event,
+		CommitID: commitID,
 		Comments: comments,
 	}
 

gitea/client_test.go

@@ -135,7 +135,7 @@ func TestPostReview(t *testing.T) {
 	defer server.Close()
 
 	client := NewClient(server.URL, "test-token")
-	review, err := client.PostReview(context.Background(), "owner", "repo", 3, "APPROVED", "LGTM", nil)
+	review, err := client.PostReview(context.Background(), "owner", "repo", 3, "APPROVED", "LGTM", "", nil)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -182,7 +182,7 @@ func TestPostReview_Non200(t *testing.T) {
 	defer server.Close()
 
 	client := NewClient(server.URL, "test-token")
-	_, err := client.PostReview(context.Background(), "owner", "repo", 1, "APPROVED", "test", nil)
+	_, err := client.PostReview(context.Background(), "owner", "repo", 1, "APPROVED", "test", "", nil)
 	if err == nil {
 		t.Fatal("expected error for 403, got nil")
 	}
@@ -1144,3 +1144,62 @@ func TestSanitizeErrorForLog(t *testing.T) {
 		})
 	}
 }
+
+func TestPostReview_CommitID_InPayload(t *testing.T) {
+	var gotPayload struct {
+		Body     string `json:"body"`
+		Event    string `json:"event"`
+		CommitID string `json:"commit_id"`
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewDecoder(r.Body).Decode(&gotPayload)
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(200)
+		json.NewEncoder(w).Encode(map[string]any{
+			"id":        200,
+			"body":      "LGTM",
+			"user":      map[string]any{"login": "bot"},
+			"state":     "APPROVED",
+			"commit_id": "deadbeef1234",
+		})
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "test-token")
+	review, err := client.PostReview(context.Background(), "owner", "repo", 5, "APPROVED", "LGTM", "deadbeef1234", nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if gotPayload.CommitID != "deadbeef1234" {
+		t.Errorf("sent commit_id = %q, want %q", gotPayload.CommitID, "deadbeef1234")
+	}
+	if review.CommitID != "deadbeef1234" {
+		t.Errorf("response commit_id = %q, want %q", review.CommitID, "deadbeef1234")
+	}
+}
+
+func TestPostReview_EmptyCommitID_OmittedFromPayload(t *testing.T) {
+	var gotRaw map[string]any
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewDecoder(r.Body).Decode(&gotRaw)
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(200)
+		json.NewEncoder(w).Encode(map[string]any{
+			"id":   201,
+			"body": "ok",
+			"user": map[string]any{"login": "bot"},
+		})
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "test-token")
+	_, err := client.PostReview(context.Background(), "owner", "repo", 5, "COMMENT", "ok", "", nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if _, exists := gotRaw["commit_id"]; exists {
+		t.Errorf("commit_id should be omitted when empty, but was present: %v", gotRaw["commit_id"])
+	}
+}

gitea/post_review_comments_test.go

@@ -37,7 +37,7 @@ func TestPostReview_WithComments(t *testing.T) {
 		{Path: "util.go", NewPosition: 10, Body: "[MINOR] Style issue"},
 	}
 
-	_, err := client.PostReview(context.Background(), "owner", "repo", 1, "REQUEST_CHANGES", "summary", comments)
+	_, err := client.PostReview(context.Background(), "owner", "repo", 1, "REQUEST_CHANGES", "summary", "", comments)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -72,7 +72,7 @@ func TestPostReview_NilComments(t *testing.T) {
 	defer server.Close()
 
 	client := NewClient(server.URL, "test-token")
-	_, err := client.PostReview(context.Background(), "owner", "repo", 1, "APPROVED", "all good", nil)
+	_, err := client.PostReview(context.Background(), "owner", "repo", 1, "APPROVED", "all good", "", nil)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}