Add test for editing the last commit of a branch in a stack

The test demonstrates that the "update-ref" todo after the selected commit is
missing, which means when we amend the commit it'll break the stack.

pkg/integration/tests/interactive_rebase/edit_last_commit_of_stacked_branch.go

@@ -0,0 +1,79 @@
+package interactive_rebase
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var EditLastCommitOfStackedBranch = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Edit and amend the last commit of a branch in a stack of branches, and ensure that it doesn't break the stack",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	GitVersion:   AtLeast("2.38.0"),
+	SetupConfig: func(config *config.AppConfig) {
+		config.GetUserConfig().Git.MainBranches = []string{"master"}
+		config.GetAppState().GitLogShowGraph = "never"
+	},
+	SetupRepo: func(shell *Shell) {
+		shell.
+			CreateNCommits(1).
+			NewBranch("branch1").
+			CreateNCommitsStartingAt(2, 2).
+			NewBranch("branch2").
+			CreateNCommitsStartingAt(2, 4)
+
+		shell.SetConfig("rebase.updateRefs", "true")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("CI commit 05").IsSelected(),
+				Contains("CI commit 04"),
+				Contains("CI * commit 03"),
+				Contains("CI commit 02"),
+				Contains("CI commit 01"),
+			).
+			NavigateToLine(Contains("commit 03")).
+			Press(keys.Universal.Edit).
+			Lines(
+				Contains("pick").Contains("CI commit 05"),
+				Contains("pick").Contains("CI commit 04"),
+				/* EXPECTED:
+				Contains("update-ref").Contains("branch1"),
+				*/
+				Contains("<-- YOU ARE HERE --- * commit 03").IsSelected(),
+				Contains("CI commit 02"),
+				Contains("CI commit 01"),
+			)
+
+		t.Shell().CreateFile("fixup-file", "fixup content")
+		t.Views().Files().
+			Focus().
+			Press(keys.Files.RefreshFiles).
+			Lines(
+				Contains("??").Contains("fixup-file").IsSelected(),
+			).
+			PressPrimaryAction().
+			Press(keys.Files.AmendLastCommit)
+		t.ExpectPopup().Confirmation().
+			Title(Equals("Amend last commit")).
+			Content(Contains("Are you sure you want to amend last commit?")).
+			Confirm()
+
+		t.Common().ContinueRebase()
+
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("CI commit 05"),
+				Contains("CI commit 04"),
+				/* EXPECTED:
+				Contains("CI * commit 03"),
+				ACTUAL: */
+				Contains("CI commit 03"),
+				Contains("CI commit 02"),
+				Contains("CI commit 01"),
+			)
+	},
+})

pkg/integration/tests/test_list.go

@@ -211,6 +211,7 @@ var tests = []*components.IntegrationTest{
 	interactive_rebase.DropTodoCommitWithUpdateRef,
 	interactive_rebase.DropWithCustomCommentChar,
 	interactive_rebase.EditFirstCommit,
+	interactive_rebase.EditLastCommitOfStackedBranch,
 	interactive_rebase.EditNonTodoCommitDuringRebase,
 	interactive_rebase.EditRangeSelectOutsideRebase,
 	interactive_rebase.EditTheConflCommit,