Add Squash merge (jesseduffield#3566)

- **PR Description**

Hello,

This PR add merge --squash. A PR already exist
jesseduffield#3130, but the author
abandoned it, so I remake it.
I modified to fit most of the comment made except this one
https://github.com/jesseduffield/lazygit/pull/3130/files#r1404808121. I
didn't find an existing example and thus didn't know to modify the code
to fit it to the new way of doing things.

There's still the choice box to commit or not to do as discussed
jesseduffield#3130 (comment).
I'll do it when I have time, I first need to read the code to see how it
really works.

Also only english has been made for now. 


![image](https://github.com/jesseduffield/lazygit/assets/94681915/f648ca13-3d16-4703-a074-a83fe9a1eb0f)


- **Please check if the PR fulfills these requirements**

* [x] Cheatsheets are up-to-date (run `go generate ./...`)
* [x] Code has been formatted (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#code-formatting))
* [x] Tests have been added/updated (see
[here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md)
for the integration test guide)
* [x] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [x] Docs (specifically `docs/Config.md`) have been updated if
necessary
* [x] You've read through your own file changes for silly mistakes etc

<!--
Be sure to name your PR with an imperative e.g. 'Add worktrees view'
see https://github.com/jesseduffield/lazygit/releases/tag/v0.40.0 for
examples
-->

docs/Config.md

@@ -283,6 +283,9 @@ git:
     # Extra args passed to `git merge`, e.g. --no-ff
     args: ""
 
+    # The commit message to use for a squash merge commit. Can contain "{{selectedRef}}" and "{{currentBranch}}" placeholders.
+    squashMergeMessage: Squash merge {{selectedRef}} into {{currentBranch}}
+
   # list of branches that are considered 'main' branches, used when displaying commits
   mainBranches:
     - master

docs/keybindings/Keybindings_en.md

@@ -162,7 +162,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` F `` | Force checkout | Force checkout selected branch. This will discard all local changes in your working directory before checking out the selected branch. |
 | `` d `` | Delete | View delete options for local/remote branch. |
 | `` r `` | Rebase | Rebase the checked-out branch onto the selected branch. |
-| `` M `` | Merge | Merge selected branch into currently checked out branch. |
+| `` M `` | Merge | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` f `` | Fast-forward | Fast-forward selected branch from its upstream. |
 | `` T `` | New tag |  |
 | `` s `` | Sort order |  |
@@ -265,7 +265,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` <c-o> `` | Copy branch name to clipboard |  |
 | `` <space> `` | Checkout | Checkout a new local branch based on the selected remote branch, or the remote branch as a detached head. |
 | `` n `` | New branch |  |
-| `` M `` | Merge | Merge selected branch into currently checked out branch. |
+| `` M `` | Merge | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` r `` | Rebase | Rebase the checked-out branch onto the selected branch. |
 | `` d `` | Delete | Delete the remote branch from the remote. |
 | `` u `` | Set as upstream | Set the selected remote branch as the upstream of the checked-out branch. |

docs/keybindings/Keybindings_ja.md

@@ -232,7 +232,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` F `` | Force checkout | Force checkout selected branch. This will discard all local changes in your working directory before checking out the selected branch. |
 | `` d `` | Delete | View delete options for local/remote branch. |
 | `` r `` | Rebase | Rebase the checked-out branch onto the selected branch. |
-| `` M `` | 現在のブランチにマージ | Merge selected branch into currently checked out branch. |
+| `` M `` | 現在のブランチにマージ | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` f `` | Fast-forward | Fast-forward selected branch from its upstream. |
 | `` T `` | タグを作成 |  |
 | `` s `` | 並び替え |  |
@@ -329,7 +329,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` <c-o> `` | ブランチ名をクリップボードにコピー |  |
 | `` <space> `` | チェックアウト | Checkout a new local branch based on the selected remote branch, or the remote branch as a detached head. |
 | `` n `` | 新しいブランチを作成 |  |
-| `` M `` | 現在のブランチにマージ | Merge selected branch into currently checked out branch. |
+| `` M `` | 現在のブランチにマージ | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` r `` | Rebase | Rebase the checked-out branch onto the selected branch. |
 | `` d `` | Delete | Delete the remote branch from the remote. |
 | `` u `` | Set as upstream | Set the selected remote branch as the upstream of the checked-out branch. |

docs/keybindings/Keybindings_ko.md

@@ -189,7 +189,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` F `` | 강제 체크아웃 | Force checkout selected branch. This will discard all local changes in your working directory before checking out the selected branch. |
 | `` d `` | Delete | View delete options for local/remote branch. |
 | `` r `` | 체크아웃된 브랜치를 이 브랜치에 리베이스 | Rebase the checked-out branch onto the selected branch. |
-| `` M `` | 현재 브랜치에 병합 | Merge selected branch into currently checked out branch. |
+| `` M `` | 현재 브랜치에 병합 | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` f `` | Fast-forward this branch from its upstream | Fast-forward selected branch from its upstream. |
 | `` T `` | 태그를 생성 |  |
 | `` s `` | Sort order |  |
@@ -242,7 +242,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` <c-o> `` | 브랜치명을 클립보드에 복사 |  |
 | `` <space> `` | 체크아웃 | Checkout a new local branch based on the selected remote branch, or the remote branch as a detached head. |
 | `` n `` | 새 브랜치 생성 |  |
-| `` M `` | 현재 브랜치에 병합 | Merge selected branch into currently checked out branch. |
+| `` M `` | 현재 브랜치에 병합 | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` r `` | 체크아웃된 브랜치를 이 브랜치에 리베이스 | Rebase the checked-out branch onto the selected branch. |
 | `` d `` | Delete | Delete the remote branch from the remote. |
 | `` u `` | Set as upstream | Set the selected remote branch as the upstream of the checked-out branch. |

docs/keybindings/Keybindings_nl.md

@@ -101,7 +101,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` F `` | Forceer checkout | Force checkout selected branch. This will discard all local changes in your working directory before checking out the selected branch. |
 | `` d `` | Delete | View delete options for local/remote branch. |
 | `` r `` | Rebase branch | Rebase the checked-out branch onto the selected branch. |
-| `` M `` | Merge in met huidige checked out branch | Merge selected branch into currently checked out branch. |
+| `` M `` | Merge in met huidige checked out branch | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` f `` | Fast-forward deze branch vanaf zijn upstream | Fast-forward selected branch from its upstream. |
 | `` T `` | Creëer tag |  |
 | `` s `` | Sort order |  |
@@ -243,7 +243,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` <c-o> `` | Kopieer branch name naar klembord |  |
 | `` <space> `` | Uitchecken | Checkout a new local branch based on the selected remote branch, or the remote branch as a detached head. |
 | `` n `` | Nieuwe branch |  |
-| `` M `` | Merge in met huidige checked out branch | Merge selected branch into currently checked out branch. |
+| `` M `` | Merge in met huidige checked out branch | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` r `` | Rebase branch | Rebase the checked-out branch onto the selected branch. |
 | `` d `` | Delete | Delete the remote branch from the remote. |
 | `` u `` | Set as upstream | Stel in als upstream van uitgecheckte branch |

docs/keybindings/Keybindings_ru.md

@@ -189,7 +189,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` F `` | Принудительное переключение | Force checkout selected branch. This will discard all local changes in your working directory before checking out the selected branch. |
 | `` d `` | Delete | View delete options for local/remote branch. |
 | `` r `` | Перебазировать переключённую ветку на эту ветку | Rebase the checked-out branch onto the selected branch. |
-| `` M `` | Слияние с текущей переключённой веткой | Merge selected branch into currently checked out branch. |
+| `` M `` | Слияние с текущей переключённой веткой | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` f `` | Перемотать эту ветку вперёд из её upstream-ветки | Fast-forward selected branch from its upstream. |
 | `` T `` | Создать тег |  |
 | `` s `` | Порядок сортировки |  |
@@ -299,7 +299,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` <c-o> `` | Скопировать название ветки в буфер обмена |  |
 | `` <space> `` | Переключить | Checkout a new local branch based on the selected remote branch, or the remote branch as a detached head. |
 | `` n `` | Новая ветка |  |
-| `` M `` | Слияние с текущей переключённой веткой | Merge selected branch into currently checked out branch. |
+| `` M `` | Слияние с текущей переключённой веткой | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` r `` | Перебазировать переключённую ветку на эту ветку | Rebase the checked-out branch onto the selected branch. |
 | `` d `` | Delete | Delete the remote branch from the remote. |
 | `` u `` | Set as upstream | Установить как upstream-ветку переключённую ветку |

docs/keybindings/Keybindings_zh-CN.md

@@ -91,7 +91,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` F `` | 强制检出 | Force checkout selected branch. This will discard all local changes in your working directory before checking out the selected branch. |
 | `` d `` | Delete | View delete options for local/remote branch. |
 | `` r `` | 将已检出的分支变基到该分支 | Rebase the checked-out branch onto the selected branch. |
-| `` M `` | 合并到当前检出的分支 | Merge selected branch into currently checked out branch. |
+| `` M `` | 合并到当前检出的分支 | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` f `` | 从上游快进此分支 | Fast-forward selected branch from its upstream. |
 | `` T `` | 创建标签 |  |
 | `` s `` | Sort order |  |
@@ -342,7 +342,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` <c-o> `` | 将分支名称复制到剪贴板 |  |
 | `` <space> `` | 检出 | Checkout a new local branch based on the selected remote branch, or the remote branch as a detached head. |
 | `` n `` | 新分支 |  |
-| `` M `` | 合并到当前检出的分支 | Merge selected branch into currently checked out branch. |
+| `` M `` | 合并到当前检出的分支 | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` r `` | 将已检出的分支变基到该分支 | Rebase the checked-out branch onto the selected branch. |
 | `` d `` | Delete | Delete the remote branch from the remote. |
 | `` u `` | Set as upstream | 设置为检出分支的上游 |

docs/keybindings/Keybindings_zh-TW.md

@@ -264,7 +264,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` F `` | 強制檢出 | Force checkout selected branch. This will discard all local changes in your working directory before checking out the selected branch. |
 | `` d `` | Delete | View delete options for local/remote branch. |
 | `` r `` | 將已檢出的分支變基至此分支 | Rebase the checked-out branch onto the selected branch. |
-| `` M `` | 合併到當前檢出的分支 | Merge selected branch into currently checked out branch. |
+| `` M `` | 合併到當前檢出的分支 | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` f `` | 從上游快進此分支 | Fast-forward selected branch from its upstream. |
 | `` T `` | 建立標籤 |  |
 | `` s `` | Sort order |  |
@@ -353,7 +353,7 @@ If you would instead like to start an interactive rebase from the selected commi
 | `` <c-o> `` | 複製分支名稱到剪貼簿 |  |
 | `` <space> `` | 檢出 | Checkout a new local branch based on the selected remote branch, or the remote branch as a detached head. |
 | `` n `` | 新分支 |  |
-| `` M `` | 合併到當前檢出的分支 | Merge selected branch into currently checked out branch. |
+| `` M `` | 合併到當前檢出的分支 | View options for merging the selected item into the current branch (regular merge, squash merge) |
 | `` r `` | 將已檢出的分支變基至此分支 | Rebase the checked-out branch onto the selected branch. |
 | `` d `` | Delete | Delete the remote branch from the remote. |
 | `` u `` | Set as upstream | 將此分支設為當前分支之上游 |

pkg/commands/git_commands/branch.go

@@ -216,13 +216,18 @@ func (self *BranchCommands) Rename(oldName string, newName string) error {
 
 type MergeOpts struct {
 	FastForwardOnly bool
+	Squash          bool
 }
 
 func (self *BranchCommands) Merge(branchName string, opts MergeOpts) error {
+	if opts.Squash && opts.FastForwardOnly {
+		panic("Squash and FastForwardOnly can't both be true")
+	}
 	cmdArgs := NewGitCmd("merge").
 		Arg("--no-edit").
 		Arg(strings.Fields(self.UserConfig.Git.Merging.Args)...).
 		ArgIf(opts.FastForwardOnly, "--ff-only").
+		ArgIf(opts.Squash, "--squash", "--ff").
 		Arg(branchName).
 		ToArgv()
 

pkg/config/user_config.go

@@ -285,6 +285,8 @@ type MergingConfig struct {
 	ManualCommit bool `yaml:"manualCommit"`
 	// Extra args passed to `git merge`, e.g. --no-ff
 	Args string `yaml:"args" jsonschema:"example=--no-ff"`
+	// The commit message to use for a squash merge commit. Can contain "{{selectedRef}}" and "{{currentBranch}}" placeholders.
+	SquashMergeMessage string `yaml:"squashMergeMessage"`
 }
 
 type LogConfig struct {
@@ -730,8 +732,9 @@ func GetDefaultConfig() *UserConfig {
 				AutoWrapWidth:         72,
 			},
 			Merging: MergingConfig{
-				ManualCommit: false,
-				Args:         "",
+				ManualCommit:       false,
+				Args:               "",
+				SquashMergeMessage: "Squash merge {{selectedRef}} into {{currentBranch}}",
 			},
 			Log: LogConfig{
 				Order:          "topo-order",

pkg/gui/controllers/branches_controller.go

@@ -111,10 +111,11 @@ func (self *BranchesController) GetKeybindings(opts types.KeybindingsOpts) []*ty
 		{
 			Key:               opts.GetKey(opts.Config.Branches.MergeIntoCurrentBranch),
 			Handler:           opts.Guards.OutsideFilterMode(self.merge),
-			GetDisabledReason: self.require(self.singleItemSelected()),
+			GetDisabledReason: self.require(self.singleItemSelected(self.notMergingIntoYourself)),
 			Description:       self.c.Tr.Merge,
 			Tooltip:           self.c.Tr.MergeBranchTooltip,
 			DisplayOnScreen:   true,
+			OpensMenu:         true,
 		},
 		{
 			Key:               opts.GetKey(opts.Config.Branches.FastForward),
@@ -826,3 +827,14 @@ func (self *BranchesController) branchIsReal(branch *models.Branch) *types.Disab
 
 	return nil
 }
+
+func (self *BranchesController) notMergingIntoYourself(branch *models.Branch) *types.DisabledReason {
+	selectedBranchName := branch.Name
+	checkedOutBranch := self.c.Helpers().Refs.GetCheckedOutRef().Name
+
+	if checkedOutBranch == selectedBranchName {
+		return &types.DisabledReason{Text: self.c.Tr.CantMergeBranchIntoItself}
+	}
+
+	return nil
+}

pkg/gui/controllers/helpers/merge_and_rebase_helper.go

@@ -369,25 +369,84 @@ func (self *MergeAndRebaseHelper) MergeRefIntoCheckedOutBranch(refName string) e
 	if checkedOutBranchName == refName {
 		return errors.New(self.c.Tr.CantMergeBranchIntoItself)
 	}
-	prompt := utils.ResolvePlaceholderString(
-		self.c.Tr.ConfirmMerge,
-		map[string]string{
-			"checkedOutBranch": checkedOutBranchName,
-			"selectedBranch":   refName,
-		},
-	)
 
-	return self.c.Confirm(types.ConfirmOpts{
-		Title:  self.c.Tr.MergeConfirmTitle,
-		Prompt: prompt,
-		HandleConfirm: func() error {
-			self.c.LogAction(self.c.Tr.Actions.Merge)
-			err := self.c.Git().Branch.Merge(refName, git_commands.MergeOpts{})
-			return self.CheckMergeOrRebase(err)
+	return self.c.Menu(types.CreateMenuOptions{
+		Title: self.c.Tr.Merge,
+		Items: []*types.MenuItem{
+			{
+				Label:   self.c.Tr.RegularMerge,
+				OnPress: self.RegularMerge(refName),
+				Key:     'm',
+				Tooltip: utils.ResolvePlaceholderString(
+					self.c.Tr.RegularMergeTooltip,
+					map[string]string{
+						"checkedOutBranch": checkedOutBranchName,
+						"selectedBranch":   refName,
+					},
+				),
+			},
+			{
+				Label:   self.c.Tr.SquashMergeUncommittedTitle,
+				OnPress: self.SquashMergeUncommitted(refName),
+				Key:     's',
+				Tooltip: utils.ResolvePlaceholderString(
+					self.c.Tr.SquashMergeUncommitted,
+					map[string]string{
+						"selectedBranch": refName,
+					},
+				),
+			},
+			{
+				Label:   self.c.Tr.SquashMergeCommittedTitle,
+				OnPress: self.SquashMergeCommitted(refName, checkedOutBranchName),
+				Key:     'S',
+				Tooltip: utils.ResolvePlaceholderString(
+					self.c.Tr.SquashMergeCommitted,
+					map[string]string{
+						"checkedOutBranch": checkedOutBranchName,
+						"selectedBranch":   refName,
+					},
+				),
+			},
 		},
 	})
 }
 
+func (self *MergeAndRebaseHelper) RegularMerge(refName string) func() error {
+	return func() error {
+		self.c.LogAction(self.c.Tr.Actions.Merge)
+		err := self.c.Git().Branch.Merge(refName, git_commands.MergeOpts{})
+		return self.CheckMergeOrRebase(err)
+	}
+}
+
+func (self *MergeAndRebaseHelper) SquashMergeUncommitted(refName string) func() error {
+	return func() error {
+		self.c.LogAction(self.c.Tr.Actions.SquashMerge)
+		err := self.c.Git().Branch.Merge(refName, git_commands.MergeOpts{Squash: true})
+		return self.CheckMergeOrRebase(err)
+	}
+}
+
+func (self *MergeAndRebaseHelper) SquashMergeCommitted(refName, checkedOutBranchName string) func() error {
+	return func() error {
+		self.c.LogAction(self.c.Tr.Actions.SquashMerge)
+		err := self.c.Git().Branch.Merge(refName, git_commands.MergeOpts{Squash: true})
+		if err = self.CheckMergeOrRebase(err); err != nil {
+			return err
+		}
+		message := utils.ResolvePlaceholderString(self.c.UserConfig.Git.Merging.SquashMergeMessage, map[string]string{
+			"selectedRef":   refName,
+			"currentBranch": checkedOutBranchName,
+		})
+		err = self.c.Git().Commit.CommitCmdObj(message, "").Run()
+		if err != nil {
+			return err
+		}
+		return self.c.Refresh(types.RefreshOptions{Mode: types.ASYNC})
+	}
+}
+
 func (self *MergeAndRebaseHelper) ResetMarkedBaseCommit() error {
 	self.c.Modes().MarkedBaseCommit.Reset()
 	return self.c.PostRefreshUpdate(self.c.Contexts().LocalCommits)