Add a test for discarding the directory of a removed submodule

If a commit that you check out or pull removes a submodule, git leaves
the submodule's directory behind, and git status reports it as an
untracked directory. The files panel shows that directory with a file
below it that has no name. Discarding the directory shows an error,
even though the directory is gone afterwards.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

pkg/integration/tests/submodule/discard_removed_submodule.go

@@ -0,0 +1,56 @@
+package submodule
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var DiscardRemovedSubmodule = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Discard the directory that a removed submodule leaves behind",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("first commit")
+		shell.CloneIntoSubmodule("sub", "modules/sub")
+		shell.Commit("add submodule")
+
+		// This is what checking out a commit that removes the submodule does:
+		// the submodule is gone from the index and from .gitmodules, but git
+		// leaves its directory behind.
+		shell.RunCommand([]string{"git", "rm", "--cached", "modules/sub"})
+		shell.RunCommand([]string{"git", "rm", ".gitmodules"})
+		shell.Commit("remove submodule")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				/* EXPECTED:
+				Equals("▼ modules").IsSelected(),
+				Equals("  ?? sub"),
+				ACTUAL: */
+				Equals("▼ modules/sub").IsSelected(),
+				Equals("  ?? "),
+			).
+			Press(keys.Universal.Remove).
+			Tap(func() {
+				t.ExpectPopup().Menu().
+					Title(Equals("Discard changes")).
+					Select(Contains("Discard all changes")).
+					Confirm()
+			}).
+			/* EXPECTED:
+			IsFocused().
+			ACTUAL: */
+			Tap(func() {
+				t.ExpectPopup().Alert().
+					Title(Equals("Error")).
+					Content(Equals("open modules/sub: no such file or directory")).
+					Confirm()
+			}).
+			IsEmpty()
+
+		t.FileSystem().PathNotPresent("modules/sub")
+	},
+})

pkg/integration/tests/test_list.go

@@ -569,6 +569,7 @@ var tests = []*components.IntegrationTest{
 	status.LogCmd,
 	status.LogCmdStatusPanelAllBranchesLog,
 	submodule.Add,
+	submodule.DiscardRemovedSubmodule,
 	submodule.Enter,
 	submodule.EnterFromDotfileBareRepo,
 	submodule.EnterNested,