Fix base64 executable not found on Windows in gh aw update

pkg/cli/download_workflow.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"encoding/base64"
 	"fmt"
 	"os"
 	"os/exec"
@@ -172,13 +173,17 @@ func downloadWorkflowContent(repo, path, ref string, verbose bool) ([]byte, erro
 	}
 
 	// The content is base64 encoded, decode it
-	contentBase64 := strings.TrimSpace(string(output))
-	base64Cmd := exec.Command("base64", "-d")
-	base64Cmd.Stdin = strings.NewReader(contentBase64)
-	content, err := base64Cmd.Output()
+	return decodeBase64FileContent(string(output))
+}
+
+// decodeBase64FileContent decodes base64-encoded file content returned by the GitHub API.
+// The GitHub API wraps lines at 60 characters and may include surrounding whitespace,
+// so both are stripped before decoding.
+func decodeBase64FileContent(raw string) ([]byte, error) {
+	cleaned := strings.ReplaceAll(strings.TrimSpace(raw), "\n", "")
+	content, err := base64.StdEncoding.DecodeString(cleaned)
 	if err != nil {
 		return nil, fmt.Errorf("failed to decode file content: %w", err)
 	}
-
 	return content, nil
 }

pkg/cli/download_workflow_test.go

@@ -0,0 +1,77 @@
+//go:build !integration
+
+package cli
+
+import (
+	"encoding/base64"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDecodeBase64FileContent(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    func() string // build the raw API-style input
+		expected string
+		wantErr  bool
+	}{
+		{
+			name: "plain base64 without newlines",
+			input: func() string {
+				return base64.StdEncoding.EncodeToString([]byte("hello world"))
+			},
+			expected: "hello world",
+		},
+		{
+			name: "GitHub API style with embedded newlines every 60 chars",
+			input: func() string {
+				encoded := base64.StdEncoding.EncodeToString([]byte("hello world"))
+				// Simulate GitHub API line-wrapping at 60 characters
+				var sb strings.Builder
+				for i, c := range encoded {
+					if i > 0 && i%60 == 0 {
+						sb.WriteByte('\n')
+					}
+					sb.WriteRune(c)
+				}
+				return sb.String()
+			},
+			expected: "hello world",
+		},
+		{
+			name: "leading and trailing whitespace stripped",
+			input: func() string {
+				return "  " + base64.StdEncoding.EncodeToString([]byte("trim me")) + "\n"
+			},
+			expected: "trim me",
+		},
+		{
+			name: "binary content round-trips correctly",
+			input: func() string {
+				data := []byte{0x00, 0x01, 0x02, 0xFF, 0xFE}
+				return base64.StdEncoding.EncodeToString(data)
+			},
+			expected: string([]byte{0x00, 0x01, 0x02, 0xFF, 0xFE}),
+		},
+		{
+			name:    "invalid base64 returns error",
+			input:   func() string { return "!!!not-valid-base64!!!" },
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := decodeBase64FileContent(tt.input())
+			if tt.wantErr {
+				assert.Error(t, err, "expected an error for invalid base64 input")
+				return
+			}
+			require.NoError(t, err, "unexpected error decoding base64 content")
+			assert.Equal(t, tt.expected, string(got), "decoded content should match expected")
+		})
+	}
+}