Fix base64 executable not found on Windows in gh aw update

[Copilot]

gh aw update fails on Windows because downloadWorkflowContent shells out to the base64 binary (unavailable on Windows) to decode GitHub API responses.

Changes

• pkg/cli/download_workflow.go: Replace exec.Command("base64", "-d") with Go's stdlib encoding/base64.StdEncoding.DecodeString(), extracting the logic into a decodeBase64FileContent helper that strips embedded newlines the GitHub API includes in its base64 payload before decoding.

• pkg/cli/download_workflow_test.go: Added unit tests for decodeBase64FileContent covering plain base64, GitHub API-style newline-wrapped content, leading/trailing whitespace stripping, binary content round-trips, and invalid input error handling.

// Before — shells out to external binary, breaks on Windows
base64Cmd := exec.Command("base64", "-d")
base64Cmd.Stdin = strings.NewReader(contentBase64)
content, err := base64Cmd.Output()

// After — pure Go, cross-platform
func decodeBase64FileContent(raw string) ([]byte, error) {
    cleaned := strings.ReplaceAll(strings.TrimSpace(raw), "\n", "")
    return base64.StdEncoding.DecodeString(cleaned)
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>"base64": executable file not found in %PATH%</issue_title>
<issue_description>
ran: gh extensions upgrade github/gh-aw

upgraded from v0.47.3 to v0.48.4

ran: gh aw upgrade

upgrade complete

ran: gh aw update

i get the error failed to download workflow: failed to decode file content: exec: "base64": executable file not found in %PATH% for all my workflows</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes "base64": executable file not found in %PATH% #17704

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[pelikhan]

@copilot add tests

[Copilot]

@copilot add tests

Added in 1aafa81. Extracted the decoding logic into a decodeBase64FileContent helper and added download_workflow_test.go with 5 table-driven tests covering: plain base64, GitHub API-style newline-wrapped content, leading/trailing whitespace, binary content round-trip, and invalid input returning an error.

[Copilot]

Pull request overview

This PR fixes a Windows compatibility issue where gh aw update fails because it shells out to the base64 command-line utility, which is not available on Windows by default. The fix replaces the external base64 command with Go's standard library encoding/base64 package for cross-platform compatibility.

Changes:

• Replaced shell command execution for base64 decoding with Go stdlib implementation
• Added comprehensive unit tests covering various edge cases including GitHub API-style newline wrapping
• Extracted decoding logic into a dedicated decodeBase64FileContent helper function

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
pkg/cli/download_workflow.go	Replaced exec.Command("base64", "-d") with stdlib base64.StdEncoding.DecodeString() and added decodeBase64FileContent helper that handles GitHub API's 60-character line wrapping
pkg/cli/download_workflow_test.go	Added comprehensive unit tests for the new decodeBase64FileContent function covering plain base64, newline-wrapped content, whitespace handling, binary data, and error cases

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.