Add a test for staging all files when there are none

The stage-all command acts on the whole file tree, and nothing stops it
from doing that when the tree is empty. It ends up in the branch that
explains why a submodule couldn't be staged, which has nothing to do
with what the user did.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/integration/tests/file/stage_all_without_changed_files.go

@@ -0,0 +1,28 @@
+package file
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var StageAllWithoutChangedFiles = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Pressing the stage-all key when there are no changed files says that there are none",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("first commit")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			IsFocused().
+			IsEmpty().
+			Press(keys.Files.ToggleStagedAll).
+			Tap(func() {
+				/* EXPECTED:
+				t.ExpectToast(Contains("No changed files"))
+				ACTUAL: */
+				t.ExpectPopup().Alert().Title(Equals("Error")).Content(Contains("Nothing to stage")).Confirm()
+			})
+	},
+})

pkg/integration/tests/test_list.go

@@ -248,6 +248,7 @@ var tests = []*components.IntegrationTest{
 	file.RenameSimilarityThresholdChange,
 	file.RenamedFiles,
 	file.RenamedFilesNoRootItem,
+	file.StageAllWithoutChangedFiles,
 	file.StageChildrenRangeSelect,
 	file.StageDeletedRangeSelect,
 	file.StageRangeSelect,