Better error message when trying to amend a commit other than head during rebase

pkg/gui/controllers/local_commits_controller.go

@@ -452,6 +452,10 @@ func (self *LocalCommitsController) amendTo(commit *models.Commit) error {
 		return self.c.Refresh(types.RefreshOptions{Mode: types.ASYNC})
 	}
 
+	if self.git.Status.WorkingTreeState() != enums.REBASE_MODE_NONE {
+		return self.c.ErrorMsg(self.c.Tr.AlreadyRebasing)
+	}
+
 	return self.c.Confirm(types.ConfirmOpts{
 		Title:  self.c.Tr.AmendCommitTitle,
 		Prompt: self.c.Tr.AmendCommitPrompt,

pkg/integration/tests/interactive_rebase/amend_non_head_commit_during_rebase.go

@@ -0,0 +1,43 @@
+package interactive_rebase
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var AmendNonHeadCommitDuringRebase = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Tries to amend a commit that is not the head while already rebasing, resulting in an error message",
+	ExtraCmdArgs: "",
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.CreateNCommits(3)
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("commit 03"),
+				Contains("commit 02"),
+				Contains("commit 01"),
+			).
+			NavigateToLine(Contains("commit 02")).
+			Press(keys.Universal.Edit).
+			Lines(
+				Contains("commit 03"),
+				Contains("<-- YOU ARE HERE --- commit 02"),
+				Contains("commit 01"),
+			)
+
+		for _, commit := range []string{"commit 01", "commit 03"} {
+			t.Views().Commits().
+				NavigateToLine(Contains(commit)).
+				Press(keys.Commits.AmendToCommit)
+
+			t.ExpectPopup().Alert().
+				Title(Equals("Error")).
+				Content(Contains("Can't perform this action during a rebase")).
+				Confirm()
+		}
+	},
+})

pkg/integration/tests/test_list.go

@@ -84,6 +84,7 @@ var tests = []*components.IntegrationTest{
 	interactive_rebase.AmendFirstCommit,
 	interactive_rebase.AmendHeadCommitDuringRebase,
 	interactive_rebase.AmendMerge,
+	interactive_rebase.AmendNonHeadCommitDuringRebase,
 	interactive_rebase.EditFirstCommit,
 	interactive_rebase.EditNonTodoCommitDuringRebase,
 	interactive_rebase.FixupFirstCommit,