Begin refactoring gui

This begins a big refactor of moving more code out of the Gui struct into contexts, controllers, and helpers. We also move some code into structs in the
gui package purely for the sake of better encapsulation

pkg/gui/controllers/switch_to_diff_files_controller.go

@@ -1,6 +1,7 @@
 package controllers
 
 import (
+	"github.com/jesseduffield/lazygit/pkg/gui/context"
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 )
 
@@ -17,20 +18,20 @@ type CanSwitchToDiffFiles interface {
 type SwitchToDiffFilesController struct {
 	baseController
 	*controllerCommon
-	context   CanSwitchToDiffFiles
-	viewFiles func(SwitchToCommitFilesContextOpts) error
+	context          CanSwitchToDiffFiles
+	diffFilesContext *context.CommitFilesContext
 }
 
 func NewSwitchToDiffFilesController(
 	controllerCommon *controllerCommon,
-	viewFiles func(SwitchToCommitFilesContextOpts) error,
 	context CanSwitchToDiffFiles,
+	diffFilesContext *context.CommitFilesContext,
 ) *SwitchToDiffFilesController {
 	return &SwitchToDiffFilesController{
 		baseController:   baseController{},
 		controllerCommon: controllerCommon,
 		context:          context,
-		viewFiles:        viewFiles,
+		diffFilesContext: diffFilesContext,
 	}
 }
 
@@ -72,3 +73,22 @@ func (self *SwitchToDiffFilesController) enter(ref types.Ref) error {
 func (self *SwitchToDiffFilesController) Context() types.Context {
 	return self.context
 }
+
+func (self *SwitchToDiffFilesController) viewFiles(opts SwitchToCommitFilesContextOpts) error {
+	diffFilesContext := self.diffFilesContext
+
+	diffFilesContext.SetSelectedLineIdx(0)
+	diffFilesContext.SetRef(opts.Ref)
+	diffFilesContext.SetTitleRef(opts.Ref.Description())
+	diffFilesContext.SetCanRebase(opts.CanRebase)
+	diffFilesContext.SetParentContext(opts.Context)
+	diffFilesContext.SetWindowName(opts.Context.GetWindowName())
+
+	if err := self.c.Refresh(types.RefreshOptions{
+		Scope: []types.RefreshableView{types.COMMIT_FILES},
+	}); err != nil {
+		return err
+	}
+
+	return self.c.PushContext(diffFilesContext)
+}