Add CmdCreaor to process and tor, allowing fully custom cmds to be

inserted

process/process.go

@@ -40,25 +40,33 @@ type Creator interface {
 	New(ctx context.Context, args ...string) (Process, error)
 }
 
+type CmdCreatorFunc func(ctx context.Context, exePath string, args ...string) (*exec.Cmd, error)
+
 type exeProcessCreator struct {
 	exePath string
+	cmdCreatorFunc CmdCreatorFunc
+}
+
+func NewCmd(ctx context.Context, exePath string, args ...string) (*exec.Cmd, error) {
+	cmd := exec.CommandContext(ctx, exePath, args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd, nil
 }
 
 // NewCreator creates a Creator for external Tor process execution based on the
 // given exe path.
-func NewCreator(exePath string) Creator {
-	return &exeProcessCreator{exePath}
+func NewCreator(exePath string, newCmd CmdCreatorFunc) Creator {
+	return &exeProcessCreator{exePath, newCmd}
 }
 
 type exeProcess struct {
 	*exec.Cmd
 }
 
 func (e *exeProcessCreator) New(ctx context.Context, args ...string) (Process, error) {
-	cmd := exec.CommandContext(ctx, e.exePath, args...)
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-	return &exeProcess{cmd}, nil
+	cmd, err := e.cmdCreatorFunc(ctx, e.exePath, args...)
+	return &exeProcess{cmd}, err
 }
 
 // ErrControlConnUnsupported is returned by Process.EmbeddedControlConn when

tor/tor.go

@@ -65,8 +65,12 @@ type StartConf struct {
 	// set.
 	ExePath string
 
+	// CmdCreatorFunc is the override to use a specific exec.Cmd. This is
+	// ignored if ProcessCreator is set
+	CmdCreator process.CmdCreatorFunc
+
 	// ProcessCreator is the override to use a specific process creator. If set,
-	// ExePath is ignored.
+	// ExePath and CmdCreator are ignored.
 	ProcessCreator process.Creator
 
 	// UseEmbeddedControlConn can be set to true to use
@@ -229,13 +233,18 @@ func createFile(to string, from io.ReadCloser) error {
 
 func (t *Tor) startProcess(ctx context.Context, conf *StartConf) error {
 	// Get the creator
+	cmdCreator := conf.CmdCreator
+	if cmdCreator == nil {
+		cmdCreator = process.NewCmd
+	}
+
 	creator := conf.ProcessCreator
 	if creator == nil {
 		torPath := conf.ExePath
 		if torPath == "" {
 			torPath = "tor"
 		}
-		creator = process.NewCreator(torPath)
+		creator = process.NewCreator(torPath, cmdCreator)
 	}
 	// Build the args
 	args := []string{"--DataDirectory", t.DataDir}