Allow squashing fixups above the first commit of a repo

This includes amending changes into a given commit, since that's implemented in
terms of the former.

pkg/commands/git_commands/rebase.go

@@ -198,12 +198,12 @@ func (self *RebaseCommands) BuildSingleActionTodo(commits []*models.Commit, acti
 }
 
 // AmendTo amends the given commit with whatever files are staged
-func (self *RebaseCommands) AmendTo(sha string) error {
+func (self *RebaseCommands) AmendTo(commit *models.Commit) error {
-	if err := self.commit.CreateFixupCommit(sha); err != nil {
+	if err := self.commit.CreateFixupCommit(commit.Sha); err != nil {
 		return err
 	}
 
-	return self.SquashAllAboveFixupCommits(sha)
+	return self.SquashAllAboveFixupCommits(commit)
 }
 
 // EditRebaseTodo sets the action at a given index in the git-rebase-todo file
@@ -258,12 +258,17 @@ func (self *RebaseCommands) MoveTodoDown(index int) error {
 }
 
 // SquashAllAboveFixupCommits squashes all fixup! commits above the given one
-func (self *RebaseCommands) SquashAllAboveFixupCommits(sha string) error {
+func (self *RebaseCommands) SquashAllAboveFixupCommits(commit *models.Commit) error {
+	shaOrRoot := commit.Sha + "^"
+	if commit.IsFirstCommit() {
+		shaOrRoot = "--root"
+	}
+
 	return self.runSkipEditorCommand(
 		self.cmd.New(
 			fmt.Sprintf(
-				"git rebase --interactive --rebase-merges --autostash --autosquash %s^",
+				"git rebase --interactive --rebase-merges --autostash --autosquash %s",
-				sha,
+				shaOrRoot,
 			),
 		),
 	)

pkg/gui/controllers/local_commits_controller.go

@@ -428,7 +428,7 @@ func (self *LocalCommitsController) amendTo(commit *models.Commit) error {
 		HandleConfirm: func() error {
 			return self.c.WithWaitingStatus(self.c.Tr.AmendingStatus, func() error {
 				self.c.LogAction(self.c.Tr.Actions.AmendCommit)
-				err := self.git.Rebase.AmendTo(commit.Sha)
+				err := self.git.Rebase.AmendTo(commit)
 				return self.helpers.MergeAndRebase.CheckMergeOrRebase(err)
 			})
 		},
@@ -571,7 +571,7 @@ func (self *LocalCommitsController) squashAllAboveFixupCommits(commit *models.Co
 		HandleConfirm: func() error {
 			return self.c.WithWaitingStatus(self.c.Tr.SquashingStatus, func() error {
 				self.c.LogAction(self.c.Tr.Actions.SquashAllAboveFixupCommits)
-				err := self.git.Rebase.SquashAllAboveFixupCommits(commit.Sha)
+				err := self.git.Rebase.SquashAllAboveFixupCommits(commit)
 				return self.helpers.MergeAndRebase.CheckMergeOrRebase(err)
 			})
 		},

pkg/integration/tests/interactive_rebase/amend_first_commit.go

@@ -0,0 +1,41 @@
+package interactive_rebase
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var AmendFirstCommit = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Amends a staged file to the first (initial) commit.",
+	ExtraCmdArgs: "",
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.
+			CreateNCommits(2).
+			CreateFileAndAdd("fixup-file", "fixup content")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("commit 02"),
+				Contains("commit 01"),
+			).
+			NavigateToListItem(Contains("commit 01")).
+			Press(keys.Commits.AmendToCommit).
+			Tap(func() {
+				t.ExpectPopup().Confirmation().
+					Title(Equals("Amend Commit")).
+					Content(Contains("Are you sure you want to amend this commit with your staged files?")).
+					Confirm()
+			}).
+			Lines(
+				Contains("commit 02"),
+				Contains("commit 01").IsSelected(),
+			)
+
+		t.Views().Main().
+			Content(Contains("fixup content"))
+	},
+})

pkg/integration/tests/interactive_rebase/squash_fixups_above_first_commit.go

@@ -0,0 +1,49 @@
+package interactive_rebase
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var SquashFixupsAboveFirstCommit = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Squashes all fixups above the first (initial) commit.",
+	ExtraCmdArgs: "",
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.
+			CreateNCommits(2).
+			CreateFileAndAdd("fixup-file", "fixup content")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("commit 02"),
+				Contains("commit 01"),
+			).
+			NavigateToListItem(Contains("commit 01")).
+			Press(keys.Commits.CreateFixupCommit).
+			Tap(func() {
+				t.ExpectPopup().Confirmation().
+					Title(Equals("Create fixup commit")).
+					Content(Contains("Are you sure you want to create a fixup! commit for commit")).
+					Confirm()
+			}).
+			NavigateToListItem(Contains("commit 01")).
+			Press(keys.Commits.SquashAboveCommits).
+			Tap(func() {
+				t.ExpectPopup().Confirmation().
+					Title(Equals("Squash all 'fixup!' commits above selected commit (autosquash)")).
+					Content(Contains("Are you sure you want to squash all fixup! commits above")).
+					Confirm()
+			}).
+			Lines(
+				Contains("commit 02"),
+				Contains("commit 01").IsSelected(),
+			)
+
+		t.Views().Main().
+			Content(Contains("fixup content"))
+	},
+})

pkg/integration/tests/tests_gen.go

@@ -65,6 +65,7 @@ var tests = []*components.IntegrationTest{
 	filter_by_path.CliArg,
 	filter_by_path.SelectFile,
 	filter_by_path.TypeFile,
+	interactive_rebase.AmendFirstCommit,
 	interactive_rebase.AmendMerge,
 	interactive_rebase.EditFirstCommit,
 	interactive_rebase.FixupFirstCommit,
@@ -73,6 +74,7 @@ var tests = []*components.IntegrationTest{
 	interactive_rebase.RewordFirstCommit,
 	interactive_rebase.SquashDownFirstCommit,
 	interactive_rebase.SquashDownSecondCommit,
+	interactive_rebase.SquashFixupsAboveFirstCommit,
 	misc.ConfirmOnQuit,
 	misc.InitialOpen,
 	patch_building.CopyPatchToClipboard,