fix(services): omit blank sha so creating a new file doesn't 422

Pushing a new file via the single-file push button failed with GitHub
HTTP 422. A 404 lookup returns sha === '' for new files, and the manual
push path (sync-manager pushFile/conflict resolution) forwarded that
empty string into the Contents API request body as "sha":"", which
GitHub rejects. Batch push avoided this via `remote.sha || undefined`.

Fix at the service layer so every caller is safe: only include sha in the
GitHub request body when it is non-empty. Apply the same guard to the
GitLab service's last_commit_id for symmetry.

Add regression tests for blank-sha pushes on both services.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DwioG4CNKUBuKiZdowLFWe

src/services/github-service.ts

@@ -39,12 +39,15 @@ export class GitHubService extends BaseGitService implements GitServiceInterface
 
     async pushFile(path: string, content: string | ArrayBuffer, branch: string, message: string, sha?: string): Promise<{ path: string, sha?: string }> {
         const url = this.getApiUrl(path);
-        const body = {
+        const body: { message: string; content: string; branch: string; sha?: string } = {
             message,
             content: this.encodeContent(content),
             branch,
-            sha
         };
+        // GitHub's Contents API rejects a blank sha with HTTP 422. Only include
+        // it when updating an existing file; a 404 lookup yields sha === '' for
+        // new files, which must be created without a sha.
+        if (sha) body.sha = sha;
 
         const response = await this.safeRequest(url, 'PUT', body);
         const data = this.parseJson<{ content: { path: string, sha: string } }>(response);

src/services/gitlab-service.ts

@@ -40,13 +40,14 @@ export class GitLabService extends BaseGitService implements GitServiceInterface
 
     async pushFile(path: string, content: string | ArrayBuffer, branch: string, message: string, sha?: string): Promise<{ path: string, sha?: string }> {
         const url = this.getApiUrl(path);
-        const body = {
+        const body: { branch: string; content: string; encoding: string; commit_message: string; last_commit_id?: string } = {
             branch,
             content: this.encodeContent(content),
             encoding: 'base64',
             commit_message: message,
-            last_commit_id: sha
         };
+        // A blank sha means the file is new: create it (POST) without last_commit_id.
+        if (sha) body.last_commit_id = sha;
 
         const method = sha ? 'PUT' : 'POST';
         const response = await this.safeRequest(url, method, body);

tests/services/github-service.test.ts

@@ -70,6 +70,21 @@ describe('GitHubService', () => {
             expect(call.body).not.toContain('"sha":');
         });
 
+        it('should omit blank sha so creating a new file does not 422', async () => {
+            // A 404 lookup yields sha === '' for new files; an empty sha sent to
+            // GitHub causes HTTP 422, so it must be dropped from the request body.
+            vi.mocked(requestUrl).mockResolvedValueOnce({
+                status: 201,
+                json: { content: { path: 'new.md', sha: 'new-sha' } }
+            } as unknown as RequestUrlResponse);
+
+            const result = await service.pushFile('new.md', 'content', 'main', 'create', '');
+
+            expect(result).toEqual({ path: 'new.md', sha: 'new-sha' });
+            const call = getLastRequestCall();
+            expect(call.body).not.toContain('"sha":');
+        });
+
         it('should update existing file correctly (sha provided)', async () => {
             mockRequest({ status: 200, json: { content: { path: 'existing.md', sha: 'updated-sha' } } });
 

tests/services/gitlab-service.test.ts

@@ -50,6 +50,14 @@ describe('GitLabService', () => {
             expect(call.body).toContain(btoa('new content'));
         });
 
+        it('should treat a blank sha as a new file (POST, no last_commit_id)', async () => {
+            mockRequest({ status: 201, json: { file_path: 'test.md' } });
+            await service.pushFile('test.md', 'new content', 'main', 'initial commit', '');
+            const call = getLastRequestCall();
+            expect(call.method).toBe('POST');
+            expect(call.body).not.toContain('last_commit_id');
+        });
+
         it('should push file content correctly (PUT for existing file)', async () => {
             mockRequest({ status: 200, json: { file_path: 'test.md' } });
             const result = await service.pushFile('test.md', 'updated content', 'main', 'update', 'old-sha');