feat: let the staging secondary panel change view mode

pkg/gui/controllers/helpers/window_arrangement_helper.go

@@ -216,6 +216,15 @@ func mainSectionChildren(args WindowArrangementArgs) []*boxlayout.Box {
 		}
 	}
 
+	if args.CurrentWindow == "secondary" && args.ScreenMode == types.SCREEN_FULL {
+		return []*boxlayout.Box{
+			{
+				Window: "secondary",
+				Weight: 1,
+			},
+		}
+	}
+
 	return []*boxlayout.Box{
 		{
 			Window: "main",
@@ -239,7 +248,7 @@ func getMidSectionWeights(args WindowArrangementArgs) (int, int) {
 		mainSectionWeight = 5 // need to shrink side panel to make way for main panels if side-by-side
 	}
 
-	if args.CurrentWindow == "main" {
+	if args.CurrentWindow == "main" || args.CurrentWindow == "secondary" {
 		if args.ScreenMode == types.SCREEN_HALF || args.ScreenMode == types.SCREEN_FULL {
 			sideSectionWeight = 0
 		}

pkg/integration/tests/staging/diff_change_screen_mode.go

@@ -0,0 +1,47 @@
+package staging
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var DiffChangeScreenMode = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Change the staged changes screen mode",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.CreateFile("file", "first line\nsecond line")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			Focus().
+			PressEnter()
+
+		t.Views().Staging().
+			IsFocused().
+			PressPrimaryAction().
+			Title(Equals("Unstaged changes")).
+			Content(Contains("+second line").DoesNotContain("+first line")).
+			PressTab()
+
+		t.Views().StagingSecondary().
+			IsFocused().
+			Title(Equals("Staged changes")).
+			Content(Contains("+first line").DoesNotContain("+second line")).
+			Press(keys.Universal.NextScreenMode).
+			Tap(func() {
+				t.Views().AppStatus().
+					IsInvisible()
+				t.Views().Staging().
+					IsVisible()
+			}).
+			Press(keys.Universal.NextScreenMode).
+			Tap(func() {
+				t.Views().AppStatus().
+					IsInvisible()
+				t.Views().Staging().
+					IsInvisible()
+			})
+	},
+})

pkg/integration/tests/test_list.go

@@ -245,6 +245,7 @@ var tests = []*components.IntegrationTest{
 	reflog.DoNotShowBranchMarkersInReflogSubcommits,
 	reflog.Patch,
 	reflog.Reset,
+	staging.DiffChangeScreenMode,
 	staging.DiffContextChange,
 	staging.DiscardAllChanges,
 	staging.Search,