[go] support bundling and auto installing the GitHub Copilot CLI (#414)

* support bundling and auto installing the GitHub Copilot CLI

* fix lint

* catch missing errors

* copilot feedback

* Potential fix for pull request finding 'Writable file handle closed without error handling'

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

* Potential fix for pull request finding 'Writable file handle closed without error handling'

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

* add --check-only

---------

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

Author: qmuntal

go/README.md

@@ -69,6 +69,18 @@ func main() {
 }
 ```
 
+## Distributing your application with an embedded GitHub Copilot CLI
+
+The SDK supports bundling, using Go's `embed` package, the Copilot CLI binary within your application's distribution.
+This allows you to bundle a specific CLI version and avoid external dependencies on the user's system.
+
+Follow these steps to embed the CLI:
+
+1. Run `go get -tool github.com/github/copilot-sdk/go/cmd/bundler`. This is a one-time setup step per project.
+2. Run `go tool bundler` in your build environment just before building your application.
+
+That's it! When your application calls `copilot.NewClient` without a `CLIPath` nor the `COPILOT_CLI_PATH` environment variable, the SDK will automatically install the embedded CLI to a cache directory and use it for all operations.
+
 ## API Reference
 
 ### Client

go/client.go

@@ -42,6 +42,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/github/copilot-sdk/go/internal/embeddedcli"
 	"github.com/github/copilot-sdk/go/internal/jsonrpc2"
 )
 
@@ -102,7 +103,7 @@ type Client struct {
 //	})
 func NewClient(options *ClientOptions) *Client {
 	opts := ClientOptions{
-		CLIPath:  "copilot",
+		CLIPath:  "",
 		Cwd:      "",
 		Port:     0,
 		LogLevel: "info",
@@ -994,6 +995,15 @@ func (c *Client) verifyProtocolVersion(ctx context.Context) error {
 // This spawns the CLI server as a subprocess using the configured transport
 // mode (stdio or TCP).
 func (c *Client) startCLIServer(ctx context.Context) error {
+	cliPath := c.options.CLIPath
+	if cliPath == "" {
+		// If no CLI path is provided, attempt to use the embedded CLI if available
+		cliPath = embeddedcli.Path()
+	}
+	if cliPath == "" {
+		// Default to "copilot" in PATH if no embedded CLI is available and no custom path is set
+		cliPath = "copilot"
+	}
 	args := []string{"--headless", "--no-auto-update", "--log-level", c.options.LogLevel}
 
 	// Choose transport mode
@@ -1020,10 +1030,10 @@ func (c *Client) startCLIServer(ctx context.Context) error {
 
 	// If CLIPath is a .js file, run it with node
 	// Note we can't rely on the shebang as Windows doesn't support it
-	command := c.options.CLIPath
-	if strings.HasSuffix(c.options.CLIPath, ".js") {
+	command := cliPath
+	if strings.HasSuffix(cliPath, ".js") {
 		command = "node"
-		args = append([]string{c.options.CLIPath}, args...)
+		args = append([]string{cliPath}, args...)
 	}
 
 	c.process = exec.CommandContext(ctx, command, args...)