Improvements to update notifier authentication

- Check for updates even if `~/.config/gh` does not exist. In this case,
  the API call is unauthenticated.

- Avoid having the update notifier ever triggering the OAuth flow.

command/root.go

@@ -66,8 +66,19 @@ var initContext = func() context.Context {
 	return ctx
 }
 
+// BasicClient returns an API client that borrows from but does not depend on
+// user configuration
 func BasicClient() (*api.Client, error) {
-	return apiClientForContext(initContext())
+	opts := []api.ClientOption{
+		api.AddHeader("User-Agent", fmt.Sprintf("GitHub CLI %s", Version)),
+	}
+	if c, err := context.ParseDefaultConfig(); err == nil {
+		opts = append(opts, api.AddHeader("Authorization", fmt.Sprintf("token %s", c.Token)))
+	}
+	if verbose := os.Getenv("DEBUG"); verbose != "" {
+		opts = append(opts, api.VerboseLog(os.Stderr))
+	}
+	return api.NewClient(opts...), nil
 }
 
 func contextForCommand(cmd *cobra.Command) context.Context {

context/config_file.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 
+	"github.com/mitchellh/go-homedir"
 	"gopkg.in/yaml.v3"
 )
 
@@ -15,18 +16,30 @@ type configEntry struct {
 	Token string `yaml:"oauth_token"`
 }
 
+func parseOrSetupConfigFile(fn string) (*configEntry, error) {
+	entry, err := parseConfigFile(fn)
+	if err != nil && errors.Is(err, os.ErrNotExist) {
+		return setupConfigFile(fn)
+	}
+	return entry, err
+}
+
 func parseConfigFile(fn string) (*configEntry, error) {
 	f, err := os.Open(fn)
 	if err != nil {
-		if errors.Is(err, os.ErrNotExist) {
-			return setupConfigFile(fn)
-		}
 		return nil, err
 	}
 	defer f.Close()
 	return parseConfig(f)
 }
 
+// ParseDefaultConfig reads the configuration from ~/.config/gh
+func ParseDefaultConfig() (*configEntry, error) {
+	// FIXME: this duplicates fsContext.configFile
+	fn, _ := homedir.Expand("~/.config/gh")
+	return parseConfigFile(fn)
+}
+
 func parseConfig(r io.Reader) (*configEntry, error) {
 	data, err := ioutil.ReadAll(r)
 	if err != nil {

context/context.go

@@ -46,7 +46,7 @@ func (c *fsContext) configFile() string {
 
 func (c *fsContext) getConfig() (*configEntry, error) {
 	if c.config == nil {
-		entry, err := parseConfigFile(c.configFile())
+		entry, err := parseOrSetupConfigFile(c.configFile())
 		if err != nil {
 			return nil, err
 		}