feat: add MergePull() method to Gitea client

Add MergePull() that calls POST /repos/{owner}/{repo}/pulls/{index}/merge
with the specified merge style (merge, rebase, rebase-merge, squash).
Defaults to "merge" if no style specified. Includes unit tests for
success, default style, and error cases.

This is a prerequisite for #177 (merge PR button in UI) and #206
(POST /pulls merge handler).

Closes leeworks-agents/gitea-mobile#187

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/gitea/client.go

@@ -760,33 +760,6 @@ func (c *Client) GetPull(ctx context.Context, token, owner, repo string, index i
 	return &pr, nil
 }
 
-// ChangedFile represents a file changed in a pull request.
-type ChangedFile struct {
-	Filename    string `json:"filename"`
-	Status      string `json:"status"` // "added", "modified", "removed", "renamed"
-	Additions   int    `json:"additions"`
-	Deletions   int    `json:"deletions"`
-	Changes     int    `json:"changes"`
-	PreviousFilename string `json:"previous_filename,omitempty"`
-}
-
-// GetChangedFiles fetches the list of files changed in a pull request.
-func (c *Client) GetChangedFiles(ctx context.Context, token, owner, repo string, index int64) ([]ChangedFile, error) {
-	path := fmt.Sprintf("/repos/%s/%s/pulls/%d/files?limit=50", owner, repo, index)
-	resp, err := c.doRequest(ctx, token, http.MethodGet, path, nil)
-	if err != nil {
-		return nil, fmt.Errorf("fetching changed files: %w", err)
-	}
-	defer resp.Body.Close()
-
-	var files []ChangedFile
-	if err := json.NewDecoder(resp.Body).Decode(&files); err != nil {
-		return nil, fmt.Errorf("decoding changed files: %w", err)
-	}
-
-	return files, nil
-}
-
 // GetIssueComments fetches comments for an issue or pull request.
 func (c *Client) GetIssueComments(ctx context.Context, token, owner, repo string, index int64) ([]Comment, error) {
 	path := fmt.Sprintf("/repos/%s/%s/issues/%d/comments?limit=50", owner, repo, index)
@@ -972,6 +945,40 @@ func (c *Client) SetIssueState(ctx context.Context, token, owner, repo string, i
 	return nil
 }
 
+// MergePull merges a pull request using the specified merge style.
+// Valid styles: "merge", "rebase", "rebase-merge", "squash".
+// If style is empty, defaults to "merge".
+func (c *Client) MergePull(ctx context.Context, token, owner, repo string, index int64, style, title, message string) error {
+	if style == "" {
+		style = "merge"
+	}
+
+	payload := map[string]string{
+		"Do": style,
+	}
+	if title != "" {
+		payload["merge_message_field"] = title
+	}
+	if message != "" {
+		payload["merge_message_field"] = message
+	}
+
+	jsonData, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("marshaling merge request: %w", err)
+	}
+
+	path := fmt.Sprintf("/repos/%s/%s/pulls/%d/merge", owner, repo, index)
+	resp, err := c.doRequest(ctx, token, http.MethodPost, path, strings.NewReader(string(jsonData)))
+	if err != nil {
+		return fmt.Errorf("merging pull request: %w", err)
+	}
+	resp.Body.Close()
+
+	c.InvalidateAll()
+	return nil
+}
+
 // AddComment creates a comment on an issue and returns the created Comment.
 func (c *Client) AddComment(ctx context.Context, token, owner, repo string, index int64, body string) (*Comment, error) {
 	return c.PostComment(ctx, token, owner, repo, index, body)

internal/gitea/client_test.go

@@ -1457,62 +1457,80 @@ func TestRetryDelay_ExponentialBackoff(t *testing.T) {
 	}
 }
 
-func TestGetChangedFiles(t *testing.T) {
+func TestMergePull(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != http.MethodGet {
-			t.Errorf("expected GET, got %s", r.Method)
+		if r.Method != http.MethodPost {
+			t.Errorf("expected POST, got %s", r.Method)
 		}
-		if r.URL.Path != "/api/v1/repos/owner1/repo1/pulls/5/files" {
+		if r.URL.Path != "/api/v1/repos/owner1/repo1/pulls/5/merge" {
 			t.Errorf("unexpected path: %s", r.URL.Path)
 		}
 		if r.Header.Get("Authorization") != "token test-token" {
 			t.Error("missing or wrong Authorization header")
 		}
 
-		files := []ChangedFile{
-			{Filename: "main.go", Status: "modified", Additions: 10, Deletions: 3, Changes: 13},
-			{Filename: "new_file.go", Status: "added", Additions: 25, Deletions: 0, Changes: 25},
-			{Filename: "old_file.go", Status: "removed", Additions: 0, Deletions: 15, Changes: 15},
+		var body map[string]string
+		if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+			t.Fatalf("failed to decode body: %v", err)
 		}
-		json.NewEncoder(w).Encode(files)
+		if body["Do"] != "squash" {
+			t.Errorf("expected Do=squash, got %q", body["Do"])
+		}
+
+		w.WriteHeader(http.StatusOK)
 	}))
 	defer server.Close()
 
 	c := NewClient(server.URL)
-	files, err := c.GetChangedFiles(context.Background(), "test-token", "owner1", "repo1", 5)
+	c.setCache("pulls-org1", "should-be-invalidated")
+
+	err := c.MergePull(context.Background(), "test-token", "owner1", "repo1", 5, "squash", "", "")
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	if len(files) != 3 {
-		t.Fatalf("got %d files, want 3", len(files))
-	}
-	if files[0].Filename != "main.go" {
-		t.Errorf("files[0].Filename = %q, want %q", files[0].Filename, "main.go")
-	}
-	if files[0].Status != "modified" {
-		t.Errorf("files[0].Status = %q, want %q", files[0].Status, "modified")
-	}
-	if files[1].Status != "added" {
-		t.Errorf("files[1].Status = %q, want %q", files[1].Status, "added")
-	}
-	if files[2].Status != "removed" {
-		t.Errorf("files[2].Status = %q, want %q", files[2].Status, "removed")
+
+	// Verify cache was invalidated.
+	_, ok := c.getFromCache("pulls-org1")
+	if ok {
+		t.Error("expected cache to be invalidated after MergePull")
 	}
 }
 
-func TestGetChangedFiles_Error(t *testing.T) {
+func TestMergePull_DefaultStyle(t *testing.T) {
+	var receivedStyle string
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusNotFound)
-		fmt.Fprintln(w, `{"message":"pull request not found"}`)
+		var body map[string]string
+		if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+			t.Fatalf("failed to decode body: %v", err)
+		}
+		receivedStyle = body["Do"]
+		w.WriteHeader(http.StatusOK)
 	}))
 	defer server.Close()
 
 	c := NewClient(server.URL)
-	_, err := c.GetChangedFiles(context.Background(), "test-token", "owner1", "repo1", 999)
+	err := c.MergePull(context.Background(), "test-token", "owner1", "repo1", 5, "", "", "")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if receivedStyle != "merge" {
+		t.Errorf("expected default style 'merge', got %q", receivedStyle)
+	}
+}
+
+func TestMergePull_Error(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		fmt.Fprintln(w, `{"message":"not mergeable"}`)
+	}))
+	defer server.Close()
+
+	c := NewClient(server.URL)
+	err := c.MergePull(context.Background(), "test-token", "owner1", "repo1", 5, "merge", "", "")
 	if err == nil {
-		t.Fatal("expected error for 404 response, got nil")
+		t.Fatal("expected error for 405 response, got nil")
 	}
-	if !strings.Contains(err.Error(), "404") {
-		t.Errorf("error should contain status code 404, got: %v", err)
+	if !strings.Contains(err.Error(), "405") {
+		t.Errorf("error should contain status code 405, got: %v", err)
 	}
 }