Avoid resolving executable() until requested at runtime

This is to avoid hitting the filesystem and resolving symlinks
unnecessarily. The value of executable is just used conditionally by a
handful of commands.

cmd/gh/main.go

@@ -236,7 +236,7 @@ func mainRun() exitCode {
 
 	newRelease := <-updateMessageChan
 	if newRelease != nil {
-		isHomebrew := isUnderHomebrew(cmdFactory.Executable)
+		isHomebrew := isUnderHomebrew(cmdFactory.Executable())
 		if isHomebrew && isRecentRelease(newRelease.PublishedAt) {
 			// do not notify Homebrew users before the version bump had a chance to get merged into homebrew-core
 			return exitOK

pkg/cmd/auth/login/login.go

@@ -38,8 +38,6 @@ func NewCmdLogin(f *cmdutil.Factory, runF func(*LoginOptions) error) *cobra.Comm
 		IO:         f.IOStreams,
 		Config:     f.Config,
 		HttpClient: f.HttpClient,
-
-		MainExecutable: f.Executable,
 	}
 
 	var tokenStdin bool
@@ -103,6 +101,7 @@ func NewCmdLogin(f *cmdutil.Factory, runF func(*LoginOptions) error) *cobra.Comm
 				}
 			}
 
+			opts.MainExecutable = f.Executable()
 			if runF != nil {
 				return runF(opts)
 			}

pkg/cmd/auth/login/login_test.go

@@ -147,7 +147,8 @@ func Test_NewCmdLogin(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			io, stdin, _, _ := iostreams.Test()
 			f := &cmdutil.Factory{
-				IOStreams: io,
+				IOStreams:  io,
+				Executable: func() string { return "/path/to/gh" },
 			}
 
 			io.SetStdoutTTY(true)

pkg/cmd/auth/refresh/refresh.go

@@ -36,7 +36,6 @@ func NewCmdRefresh(f *cmdutil.Factory, runF func(*RefreshOptions) error) *cobra.
 			_, err := authflow.AuthFlowWithConfig(cfg, io, hostname, "", scopes)
 			return err
 		},
-		MainExecutable: f.Executable,
 	}
 
 	cmd := &cobra.Command{
@@ -62,6 +61,7 @@ func NewCmdRefresh(f *cmdutil.Factory, runF func(*RefreshOptions) error) *cobra.
 				return &cmdutil.FlagError{Err: errors.New("--hostname required when not running interactively")}
 			}
 
+			opts.MainExecutable = f.Executable()
 			if runF != nil {
 				return runF(opts)
 			}

pkg/cmd/auth/refresh/refresh_test.go

@@ -88,7 +88,8 @@ func Test_NewCmdRefresh(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			io, _, _, _ := iostreams.Test()
 			f := &cmdutil.Factory{
-				IOStreams: io,
+				IOStreams:  io,
+				Executable: func() string { return "/path/to/gh" },
 			}
 			io.SetStdinTTY(tt.tty)
 			io.SetStdoutTTY(tt.tty)

pkg/cmd/factory/default.go

@@ -19,12 +19,17 @@ import (
 )
 
 func New(appVersion string) *cmdutil.Factory {
+	var exe string
 	f := &cmdutil.Factory{
-		Config:     configFunc(),     // No factory dependencies
-		Branch:     branchFunc(),     // No factory dependencies
-		Executable: executable("gh"), // No factory dependencies
-
-		ExtensionManager: extension.NewManager(),
+		Config: configFunc(), // No factory dependencies
+		Branch: branchFunc(), // No factory dependencies
+		Executable: func() string {
+			if exe != "" {
+				return exe
+			}
+			exe = executable("gh")
+			return exe
+		},
 	}
 
 	f.IOStreams = ioStreams(f)                   // Depends on Config

pkg/cmdutil/factory.go

@@ -27,5 +27,5 @@ type Factory struct {
 	ExtensionManager extensions.ExtensionManager
 
 	// Executable is the path to the currently invoked gh binary
-	Executable string
+	Executable func() string
 }