test(file_write_branch): cover POST-on-create and PUT-on-update routing

internal/tools/file_write_branch_test.go

@@ -39,9 +39,9 @@ func TestFileWriteBranchCreatesBranchAndFile(t *testing.T) {
 		_, _ = w.Write([]byte(createBranchResp))
 	})
 
-	// Upsert file → 201
+	// New file (no sha) → POST to /contents/{path}
 	mux.HandleFunc("/api/v1/repos/owner/myrepo/contents/doc.md", func(w http.ResponseWriter, r *http.Request) {
-		require.Equal(t, http.MethodPut, r.Method)
+		require.Equal(t, http.MethodPost, r.Method)
 		w.WriteHeader(http.StatusCreated)
 		_, _ = w.Write([]byte(upsertFileResp))
 	})
@@ -64,6 +64,35 @@ func TestFileWriteBranchCreatesBranchAndFile(t *testing.T) {
 	assert.Equal(t, "cmt1", result["commit_sha"])
 }
 
+func TestFileWriteBranchUsesPutWhenShaProvided(t *testing.T) {
+	mux := http.NewServeMux()
+
+	// Branch exists
+	mux.HandleFunc("/api/v1/repos/owner/myrepo/branches/feat/existing", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(branchCheckExistsResp))
+	})
+
+	// Existing file (sha provided) → PUT
+	mux.HandleFunc("/api/v1/repos/owner/myrepo/contents/doc.md", func(w http.ResponseWriter, r *http.Request) {
+		require.Equal(t, http.MethodPut, r.Method)
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(upsertFileResp))
+	})
+
+	srv := httptest.NewServer(mux)
+	defer srv.Close()
+
+	tool := tools.NewFileWriteBranch(gitea.NewClient(srv.URL, "tok"), allowlist.New([]string{"owner"}))
+	out, err := tool.Call(context.Background(), json.RawMessage(`{
+		"owner":"owner","name":"myrepo","path":"doc.md",
+		"content":"hello","branch":"feat/existing",
+		"sha":"oldsha","message":"update doc.md"
+	}`))
+	require.NoError(t, err)
+	require.NotNil(t, out)
+}
+
 func TestFileWriteBranchUsesDefaultBaseWhenBaseEmpty(t *testing.T) {
 	var createBody []byte
 	mux := http.NewServeMux()