Fix flaky integration test (#4432)

- **PR Description**

The integration test `stash/rename.go` occasionally fails for me
locally. This PR fixes it.

In 8b8343b8a9 we made a change to run newPtyTask from AfterLayout; this
is needed so that the PTY gets the new, updated view size. However, this
created a race condition for integration tests that select a line in a
list view and then expect the main view to have certain content;
sometimes that content gets rendered too late.

I'm surprised that this didn't cause more tests to fail; right now I
only know of one test that occasionally fails because of this, which is
`stash/rename.go`.

Fix this by moving the AfterLayout to inside newPtyTask, and do it only
when we are actually using a PTY (we don't when no pager is configured,
which is the case for integration tests).

The diff is best viewed with "ignore whitespace" turned on.

pkg/gui/main_panels.go

@@ -20,10 +20,7 @@ func (gui *Gui) runTaskForView(view *gocui.View, task types.UpdateTask) error {
 		return gui.newCmdTask(view, v.Cmd, v.Prefix)
 
 	case *types.RunPtyTask:
-		gui.afterLayout(func() error {
 		return gui.newPtyTask(view, v.Cmd, v.Prefix)
-		})
-		return nil
 	}
 
 	return nil

pkg/gui/pty.go

@@ -54,6 +54,13 @@ func (gui *Gui) newPtyTask(view *gocui.View, cmd *exec.Cmd, prefix string) error
 		return gui.newCmdTask(view, cmd, prefix)
 	}
 
+	// Run the pty after layout so that it gets the correct size
+	gui.afterLayout(func() error {
+		// Need to get the width and the pager again because the layout might have
+		// changed the size of the view
+		width = view.InnerWidth()
+		pager = gui.git.Config.GetPager(width)
+
 		cmdStr := strings.Join(cmd.Args, " ")
 
 		// This communicates to pagers that we're in a very simple
@@ -90,9 +97,8 @@ func (gui *Gui) newPtyTask(view *gocui.View, cmd *exec.Cmd, prefix string) error
 		}
 
 		linesToRead := gui.linesToReadFromCmdTask(view)
-	if err := manager.NewTask(manager.NewCmdTask(start, prefix, linesToRead, onClose), cmdStr); err != nil {
+		return manager.NewTask(manager.NewCmdTask(start, prefix, linesToRead, onClose), cmdStr)
-		return err
+	})
-	}
 
 	return nil
 }