Close piped processes on cancellation

internal/process/process.go

@@ -55,6 +55,8 @@ type PipedProcess struct {
 	stdout   io.ReadCloser
 	parent   context.Context
 	cancel   context.CancelFunc
+	stopIO   func() bool
+	ioDone   <-chan struct{}
 	waitOnce sync.Once
 	waitErr  error
 }
@@ -80,6 +82,9 @@ func (child *PipedProcess) Cancel() {
 func (child *PipedProcess) Wait() error {
 	child.waitOnce.Do(func() {
 		err := child.command.Wait()
+		if !child.stopIO() {
+			<-child.ioDone
+		}
 		child.cancel()
 		if err == nil {
 			return
@@ -121,12 +126,20 @@ func StartPiped(ctx context.Context, invocation Invocation) (*PipedProcess, erro
 		cancel()
 		return nil, fmt.Errorf("start %q: %w", invocation.Args[0], err)
 	}
+	done := make(chan struct{})
+	stopIO := context.AfterFunc(childContext, func() {
+		defer close(done)
+		_ = stdin.Close()
+		_ = stdout.Close()
+	})
 	return &PipedProcess{
 		command: command,
 		stdin:   stdin,
 		stdout:  stdout,
 		parent:  ctx,
 		cancel:  cancel,
+		stopIO:  stopIO,
+		ioDone:  done,
 	}, nil
 }