Add merge options menu

Replace merge-tool with merge options menu that allows resolving all
conflicts for selected files as ours, theirs, or union, while still
providing access to the merge tool.

docs/Config.md

@@ -619,7 +619,7 @@ keybinding:
     viewResetOptions: D
     fetch: f
     toggleTreeView: '`'
-    openMergeTool: M
+    openMergeOptions: M
     openStatusFilter: <c-b>
     copyFileInfoToClipboard: "y"
     collapseAll: '-'

docs/keybindings/Keybindings_en.md

@@ -153,7 +153,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` D `` | Reset | View reset options for working tree (e.g. nuking the working tree). |
 | `` ` `` | Toggle file tree view | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | Open external diff tool (git difftool) |  |
-| `` M `` | Open external merge tool | Run `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | Fetch | Fetch changes from remote. |
 | `` - `` | Collapse all files | Collapse all directories in the files tree |
 | `` = `` | Expand all files | Expand all directories in the file tree |
@@ -210,7 +210,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` z `` | Undo | Undo last merge conflict resolution. |
 | `` e `` | Edit file | Open file in external editor. |
 | `` o `` | Open file | Open file in default application. |
-| `` M `` | Open external merge tool | Run `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | Return to files panel |  |
 
 ## Main panel (normal)

docs/keybindings/Keybindings_ja.md

@@ -235,7 +235,7 @@ _凡例：`＜c-b＞` はctrl+b、`＜a-b＞` はalt+b、`B` はshift+bを意味
 | `` D `` | リセット | 作業ツリーのリセットオプション（例：作業ツリーの完全破棄）を表示します。 |
 | `` ` `` | ファイルツリービューを切り替え | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | 外部差分ツールを開く（git difftool） |  |
-| `` M `` | 外部マージツールを開く | `git mergetool`を実行します。 |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | フェッチ | リモートから変更をフェッチします。 |
 | `` - `` | すべてのファイルを折りたたむ | ファイルツリー内のすべてのディレクトリを折りたたみます |
 | `` = `` | すべてのファイルを展開 | ファイルツリー内のすべてのディレクトリを展開します |
@@ -292,7 +292,7 @@ _凡例：`＜c-b＞` はctrl+b、`＜a-b＞` はalt+b、`B` はshift+bを意味
 | `` z `` | 元に戻す | 最後のマージコンフリクト解決を元に戻します。 |
 | `` e `` | ファイルを編集 | 外部エディタでファイルを開きます。 |
 | `` o `` | ファイルを開く | デフォルトのアプリケーションでファイルを開きます。 |
-| `` M `` | 外部マージツールを開く | `git mergetool`を実行します。 |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | ファイルパネルに戻る |  |
 
 ## メインパネル（通常）

docs/keybindings/Keybindings_ko.md

@@ -152,7 +152,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` z `` | 되돌리기 | Undo last merge conflict resolution. |
 | `` e `` | 파일 편집 | Open file in external editor. |
 | `` o `` | 파일 닫기 | Open file in default application. |
-| `` M `` | Git mergetool를 열기 | Run `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | 파일 목록으로 돌아가기 |  |
 
 ## 메인 패널 (Normal)
@@ -396,7 +396,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` D `` | 초기화 | View reset options for working tree (e.g. nuking the working tree). |
 | `` ` `` | 파일 트리뷰로 전환 | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | Open external diff tool (git difftool) |  |
-| `` M `` | Git mergetool를 열기 | Run `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | Fetch | Fetch changes from remote. |
 | `` - `` | Collapse all files | Collapse all directories in the files tree |
 | `` = `` | Expand all files | Expand all directories in the file tree |

docs/keybindings/Keybindings_nl.md

@@ -78,7 +78,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` D `` | Reset | View reset options for working tree (e.g. nuking the working tree). |
 | `` ` `` | Toggle bestandsboom weergave | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | Open external diff tool (git difftool) |  |
-| `` M `` | Open external merge tool | Run `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | Fetch | Fetch changes from remote. |
 | `` - `` | Collapse all files | Collapse all directories in the files tree |
 | `` = `` | Expand all files | Expand all directories in the file tree |
@@ -218,7 +218,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` z `` | Ongedaan maken | Undo last merge conflict resolution. |
 | `` e `` | Verander bestand | Open file in external editor. |
 | `` o `` | Open bestand | Open file in default application. |
-| `` M `` | Open external merge tool | Run `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | Ga terug naar het bestanden paneel |  |
 
 ## Normaal

docs/keybindings/Keybindings_pl.md

@@ -193,7 +193,7 @@ _Legenda: `<c-b>` oznacza ctrl+b, `<a-b>` oznacza alt+b, `B` oznacza shift+b_
 | `` z `` | Cofnij | Cofnij ostatnie rozwiązanie konfliktu scalania. |
 | `` e `` | Edytuj plik | Otwórz plik w zewnętrznym edytorze. |
 | `` o `` | Otwórz plik | Otwórz plik w domyślnej aplikacji. |
-| `` M `` | Otwórz zewnętrzne narzędzie scalania | Uruchom `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | Wróć do panelu plików |  |
 
 ## Panel główny (zatwierdzanie)
@@ -252,7 +252,7 @@ _Legenda: `<c-b>` oznacza ctrl+b, `<a-b>` oznacza alt+b, `B` oznacza shift+b_
 | `` D `` | Reset | Wyświetl opcje resetu dla drzewa roboczego (np. zniszczenie drzewa roboczego). |
 | `` ` `` | Przełącz widok drzewa plików | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | Otwórz zewnętrzne narzędzie różnic (git difftool) |  |
-| `` M `` | Otwórz zewnętrzne narzędzie scalania | Uruchom `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | Pobierz | Pobierz zmiany ze zdalnego serwera. |
 | `` - `` | Collapse all files | Collapse all directories in the files tree |
 | `` = `` | Expand all files | Expand all directories in the file tree |

docs/keybindings/Keybindings_pt.md

@@ -78,7 +78,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` D `` | Restaurar | Opções de redefinição de exibição para árvore de trabalho (por exemplo, nukando a árvore de trabalho). |
 | `` ` `` | Alternar exibição de árvore de arquivo | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | Abrir ferramenta de diff externa (git difftool) |  |
-| `` M `` | Abrir ferramenta de merge externa | Execute `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | Buscar | Buscar alterações do controle remoto. |
 | `` - `` | Recolher todos os arquivos | Recolher todos os diretórios na árvore de arquivos |
 | `` = `` | Expandir todos os arquivos | Expandir todos os diretórios na árvore do arquivo |
@@ -278,7 +278,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 | `` z `` | Desfazer | Desfazer resolução de conflitos de última mesclagem. |
 | `` e `` | Editar arquivo | Abrir arquivo no editor externo. |
 | `` o `` | Abrir arquivo | Abrir arquivo no aplicativo padrão. |
-| `` M `` | Abrir ferramenta de merge externa | Execute `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | Retornar ao painel de arquivos |  |
 
 ## Painel principal (patch build)

docs/keybindings/Keybindings_ru.md

@@ -122,7 +122,7 @@ _Связки клавиш_
 | `` z `` | Отменить | Undo last merge conflict resolution. |
 | `` e `` | Редактировать файл | Open file in external editor. |
 | `` o `` | Открыть файл | Open file in default application. |
-| `` M `` | Открыть внешний инструмент слияния (git mergetool) | Run `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | Вернуться к панели файлов |  |
 
 ## Главная панель (сборка патчей)
@@ -390,7 +390,7 @@ _Связки клавиш_
 | `` D `` | Reset | View reset options for working tree (e.g. nuking the working tree). |
 | `` ` `` | Переключить вид дерева файлов | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | Open external diff tool (git difftool) |  |
-| `` M `` | Открыть внешний инструмент слияния (git mergetool) | Run `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | Получить изменения | Fetch changes from remote. |
 | `` - `` | Collapse all files | Collapse all directories in the files tree |
 | `` = `` | Expand all files | Expand all directories in the file tree |

docs/keybindings/Keybindings_zh-CN.md

@@ -216,7 +216,7 @@ _图例：`<c-b>` 意味着ctrl+b, `<a-b>意味着Alt+b, `B` 意味着shift+b_
 | `` D `` | 重置 | 查看工作树的重置选项（例如：清除工作树）。 |
 | `` ` `` | 切换文件树视图 | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | 使用外部差异比较工具(git difftool) |  |
-| `` M `` | 打开外部合并工具(git mergetool) | 执行 `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | 抓取 | 从远程获取变更 |
 | `` - `` | 折叠全部文件 | 折叠文件树中的全部目录 |
 | `` = `` | 展开全部文件 | 展开文件树中的全部目录 |
@@ -305,7 +305,7 @@ _图例：`<c-b>` 意味着ctrl+b, `<a-b>意味着Alt+b, `B` 意味着shift+b_
 | `` z `` | 撤销 | 撤消上次合并冲突解决 |
 | `` e `` | 编辑文件 | 使用外部编辑器打开文件 |
 | `` o `` | 打开文件 | 使用默认程序打开该文件 |
-| `` M `` | 打开外部合并工具(git mergetool) | 执行 `git mergetool`. |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | 返回文件面板 |  |
 
 ## 正在暂存

docs/keybindings/Keybindings_zh-TW.md

@@ -97,7 +97,7 @@ _說明：`<c-b>` 表示 Ctrl＋B、`<a-b>` 表示 Alt＋B，`B`表示 Shift＋B
 | `` z `` | 復原 | Undo last merge conflict resolution. |
 | `` e `` | 編輯檔案 | 使用外部編輯器開啟 |
 | `` o `` | 開啟檔案 | 使用預設軟體開啟 |
-| `` M `` | 開啟外部合併工具 | 執行 `git mergetool`。 |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` <esc> `` | 返回檔案面板 |  |
 
 ## 主面板（預存）
@@ -347,7 +347,7 @@ _說明：`<c-b>` 表示 Ctrl＋B、`<a-b>` 表示 Alt＋B，`B`表示 Shift＋B
 | `` D `` | 重設 | View reset options for working tree (e.g. nuking the working tree). |
 | `` ` `` | 顯示檔案樹狀視圖 | Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.<br><br>The default can be changed in the config file with the key 'gui.showFileTree'. |
 | `` <c-t> `` | 開啟外部差異工具 (git difftool) |  |
-| `` M `` | 開啟外部合併工具 | 執行 `git mergetool`。 |
+| `` M `` | View merge conflict options | View options for resolving merge conflicts. |
 | `` f `` | 擷取 | 同步遠端異動 |
 | `` - `` | Collapse all files | Collapse all directories in the files tree |
 | `` = `` | Expand all files | Expand all directories in the file tree |

pkg/commands/git_commands/working_tree.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"strings"
 
 	"github.com/go-errors/errors"
 	"github.com/jesseduffield/lazygit/pkg/commands/models"
@@ -407,3 +408,46 @@ func (self *WorkingTreeCommands) ResetMixed(ref string) error {
 
 	return self.cmd.New(cmdArgs).Run()
 }
+
+func (self *WorkingTreeCommands) ShowFileAtStage(path string, stage int) (string, error) {
+	cmdArgs := NewGitCmd("show").
+		Arg(fmt.Sprintf(":%d:%s", stage, path)).
+		ToArgv()
+
+	return self.cmd.New(cmdArgs).RunWithOutput()
+}
+
+func (self *WorkingTreeCommands) ObjectIDAtStage(path string, stage int) (string, error) {
+	cmdArgs := NewGitCmd("rev-parse").
+		Arg(fmt.Sprintf(":%d:%s", stage, path)).
+		ToArgv()
+
+	output, err := self.cmd.New(cmdArgs).RunWithOutput()
+	if err != nil {
+		return "", err
+	}
+
+	return strings.TrimSpace(output), nil
+}
+
+func (self *WorkingTreeCommands) MergeFileForFiles(strategy string, oursFilepath string, baseFilepath string, theirsFilepath string) (string, error) {
+	cmdArgs := NewGitCmd("merge-file").
+		Arg(strategy).
+		Arg("--stdout").
+		Arg(oursFilepath, baseFilepath, theirsFilepath).
+		ToArgv()
+
+	return self.cmd.New(cmdArgs).RunWithOutput()
+}
+
+// OIDs mode (Git 2.43+)
+func (self *WorkingTreeCommands) MergeFileForObjectIDs(strategy string, oursID string, baseID string, theirsID string) (string, error) {
+	cmdArgs := NewGitCmd("merge-file").
+		Arg(strategy).
+		Arg("--stdout").
+		Arg("--object-id").
+		Arg(oursID, baseID, theirsID).
+		ToArgv()
+
+	return self.cmd.New(cmdArgs).RunWithOutput()
+}

pkg/config/app_config.go

@@ -272,6 +272,7 @@ func computeMigratedConfig(path string, content []byte, changes *ChangesSet) ([]
 		{[]string{"gui", "skipUnstageLineWarning"}, "skipDiscardChangeWarning"},
 		{[]string{"keybinding", "universal", "executeCustomCommand"}, "executeShellCommand"},
 		{[]string{"gui", "windowSize"}, "screenMode"},
+		{[]string{"keybinding", "files", "openMergeTool"}, "openMergeOptions"},
 	}
 
 	for _, pathToReplace := range pathsToReplace {

pkg/config/app_config_test.go

@@ -897,7 +897,7 @@ keybinding:
     toggleStagedAll: a
     viewResetOptions: D
     fetch: f
-    openMergeTool: M
+    openMergeOptions: M
     openStatusFilter: <c-b>
     copyFileInfoToClipboard: "y"
     collapseAll: '-'

pkg/config/user_config.go

@@ -487,7 +487,7 @@ type KeybindingFilesConfig struct {
 	ViewResetOptions         string `yaml:"viewResetOptions"`
 	Fetch                    string `yaml:"fetch"`
 	ToggleTreeView           string `yaml:"toggleTreeView"`
-	OpenMergeTool            string `yaml:"openMergeTool"`
+	OpenMergeOptions         string `yaml:"openMergeOptions"`
 	OpenStatusFilter         string `yaml:"openStatusFilter"`
 	CopyFileInfoToClipboard  string `yaml:"copyFileInfoToClipboard"`
 	CollapseAll              string `yaml:"collapseAll"`
@@ -950,7 +950,7 @@ func GetDefaultConfig() *UserConfig {
 				ViewResetOptions:         "D",
 				Fetch:                    "f",
 				ToggleTreeView:           "`",
-				OpenMergeTool:            "M",
+				OpenMergeOptions:         "M",
 				OpenStatusFilter:         "<c-b>",
 				ConfirmDiscard:           "x",
 				CopyFileInfoToClipboard:  "y",

pkg/gui/command_log_panel.go

@@ -124,8 +124,8 @@ func (gui *Gui) getRandomTip() string {
 			formattedKey(config.Universal.Remove),
 		),
 		fmt.Sprintf(
-			"If you need to pull out the big guns to resolve merge conflicts, you can press '%s' in the files panel to open 'git mergetool'",
-			formattedKey(config.Files.OpenMergeTool),
+			"If you need to pull out the big guns to resolve merge conflicts, you can press '%s' in the files panel to open merge options",
+			formattedKey(config.Files.OpenMergeOptions),
 		),
 		fmt.Sprintf(
 			"To revert a commit, press '%s' on that commit",

pkg/gui/controllers.go

@@ -98,7 +98,7 @@ func (gui *Gui) resetHelpersAndControllers() {
 		Bisect:          bisectHelper,
 		Suggestions:     suggestionsHelper,
 		Files:           helpers.NewFilesHelper(helperCommon),
-		WorkingTree:     helpers.NewWorkingTreeHelper(helperCommon, refsHelper, commitsHelper, gpgHelper),
+		WorkingTree:     helpers.NewWorkingTreeHelper(helperCommon, refsHelper, commitsHelper, gpgHelper, rebaseHelper),
 		Tags:            helpers.NewTagsHelper(helperCommon, commitsHelper, gpgHelper),
 		BranchesHelper:  helpers.NewBranchesHelper(helperCommon, worktreeHelper),
 		GPG:             helpers.NewGpgHelper(helperCommon),

pkg/gui/controllers/files_controller.go

@@ -178,10 +178,13 @@ func (self *FilesController) GetKeybindings(opts types.KeybindingsOpts) []*types
 			Description:       self.c.Tr.OpenDiffTool,
 		},
 		{
-			Key:         opts.GetKey(opts.Config.Files.OpenMergeTool),
-			Handler:     self.c.Helpers().WorkingTree.OpenMergeTool,
-			Description: self.c.Tr.OpenMergeTool,
-			Tooltip:     self.c.Tr.OpenMergeToolTooltip,
+			Key:               opts.GetKey(opts.Config.Files.OpenMergeOptions),
+			Handler:           self.withItems(self.openMergeConflictMenu),
+			Description:       self.c.Tr.ViewMergeConflictOptions,
+			Tooltip:           self.c.Tr.ViewMergeConflictOptionsTooltip,
+			GetDisabledReason: self.require(self.itemsSelected(self.canOpenMergeConflictMenu)),
+			OpensMenu:         true,
+			DisplayOnScreen:   true,
 		},
 		{
 			Key:         opts.GetKey(opts.Config.Files.Fetch),
@@ -1024,6 +1027,34 @@ func (self *FilesController) createStashMenu() error {
 	})
 }
 
+func (self *FilesController) openMergeConflictMenu(nodes []*filetree.FileNode) error {
+	normalizedNodes := flattenSelectedNodesToFiles(nodes)
+
+	fileNodesWithConflicts := lo.Filter(normalizedNodes, func(node *filetree.FileNode, _ int) bool {
+		return node.File != nil && node.File.HasInlineMergeConflicts
+	})
+
+	filepaths := lo.Map(fileNodesWithConflicts, func(node *filetree.FileNode, _ int) string {
+		return node.GetPath()
+	})
+
+	return self.c.Helpers().WorkingTree.CreateMergeConflictMenu(filepaths)
+}
+
+func (self *FilesController) canOpenMergeConflictMenu(nodes []*filetree.FileNode) *types.DisabledReason {
+	normalizedNodes := flattenSelectedNodesToFiles(nodes)
+
+	hasFileNodesWithConflicts := lo.SomeBy(normalizedNodes, func(node *filetree.FileNode) bool {
+		return node.File != nil && node.File.HasInlineMergeConflicts
+	})
+
+	if !hasFileNodesWithConflicts {
+		return &types.DisabledReason{Text: self.c.Tr.NoFilesWithMergeConflicts}
+	}
+
+	return nil
+}
+
 func (self *FilesController) openCopyMenu() error {
 	node := self.context().GetSelected()
 
@@ -1237,6 +1268,38 @@ func isDescendentOfSelectedNodes(node *filetree.FileNode, selectedNodes []*filet
 	return false
 }
 
+// BFS algorithm for expanding directories into their children,
+// and for collecting the unique file nodes
+func flattenSelectedNodesToFiles(selectedNodes []*filetree.FileNode) []*filetree.FileNode {
+	queue := append(make([]*filetree.FileNode, 0, len(selectedNodes)), selectedNodes...)
+	visited := set.New[string]()
+	var files []*filetree.FileNode
+
+	for len(queue) > 0 {
+		// pop node from queue
+		node := queue[0]
+		queue = queue[1:]
+
+		nodeID := node.ID()
+		if visited.Includes(nodeID) {
+			continue
+		}
+		visited.Add(nodeID)
+
+		if node.File != nil {
+			// unique file node -> collect it
+			files = append(files, node)
+			continue
+		}
+
+		// directory node -> enqueue children
+		for _, ch := range node.Children {
+			queue = append(queue, &filetree.FileNode{Node: ch})
+		}
+	}
+	return files
+}
+
 func someNodesHaveUnstagedChanges(nodes []*filetree.FileNode) bool {
 	return lo.SomeBy(nodes, (*filetree.FileNode).GetHasUnstagedChanges)
 }

pkg/gui/controllers/helpers/working_tree_helper.go

@@ -3,21 +3,24 @@ package helpers
 import (
 	"errors"
 	"fmt"
+	"os"
 	"regexp"
 
 	"github.com/jesseduffield/lazygit/pkg/commands/git_commands"
 	"github.com/jesseduffield/lazygit/pkg/commands/models"
 	"github.com/jesseduffield/lazygit/pkg/config"
 	"github.com/jesseduffield/lazygit/pkg/gui/context"
+	"github.com/jesseduffield/lazygit/pkg/gui/style"
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 	"github.com/samber/lo"
 )
 
 type WorkingTreeHelper struct {
-	c             *HelperCommon
-	refHelper     *RefsHelper
-	commitsHelper *CommitsHelper
-	gpgHelper     *GpgHelper
+	c                    *HelperCommon
+	refHelper            *RefsHelper
+	commitsHelper        *CommitsHelper
+	gpgHelper            *GpgHelper
+	mergeAndRebaseHelper *MergeAndRebaseHelper
 }
 
 func NewWorkingTreeHelper(
@@ -25,12 +28,14 @@ func NewWorkingTreeHelper(
 	refHelper *RefsHelper,
 	commitsHelper *CommitsHelper,
 	gpgHelper *GpgHelper,
+	mergeAndRebaseHelper *MergeAndRebaseHelper,
 ) *WorkingTreeHelper {
 	return &WorkingTreeHelper{
-		c:             c,
-		refHelper:     refHelper,
-		commitsHelper: commitsHelper,
-		gpgHelper:     gpgHelper,
+		c:                    c,
+		refHelper:            refHelper,
+		commitsHelper:        commitsHelper,
+		gpgHelper:            gpgHelper,
+		mergeAndRebaseHelper: mergeAndRebaseHelper,
 	}
 }
 
@@ -247,3 +252,135 @@ func (self *WorkingTreeHelper) commitPrefixConfigsForRepo() []config.CommitPrefi
 
 	return self.c.UserConfig().Git.CommitPrefix
 }
+
+func (self *WorkingTreeHelper) mergeFile(filepath string, strategy string) (string, error) {
+	if self.c.Git().Version.IsOlderThan(2, 43, 0) {
+		return self.mergeFileWithTempFiles(filepath, strategy)
+	}
+
+	return self.mergeFileWithObjectIDs(filepath, strategy)
+}
+
+func (self *WorkingTreeHelper) mergeFileWithTempFiles(filepath string, strategy string) (string, error) {
+	showToTempFile := func(stage int, label string) (string, error) {
+		output, err := self.c.Git().WorkingTree.ShowFileAtStage(filepath, stage)
+		if err != nil {
+			return "", err
+		}
+
+		f, err := os.CreateTemp(self.c.GetConfig().GetTempDir(), "mergefile-"+label+"-*")
+		if err != nil {
+			return "", err
+		}
+		defer f.Close()
+
+		if _, err := f.Write([]byte(output)); err != nil {
+			return "", err
+		}
+
+		return f.Name(), nil
+	}
+
+	baseFilepath, err := showToTempFile(1, "base")
+	if err != nil {
+		return "", err
+	}
+	defer os.Remove(baseFilepath)
+
+	oursFilepath, err := showToTempFile(2, "ours")
+	if err != nil {
+		return "", err
+	}
+	defer os.Remove(oursFilepath)
+
+	theirsFilepath, err := showToTempFile(3, "theirs")
+	if err != nil {
+		return "", err
+	}
+	defer os.Remove(theirsFilepath)
+
+	return self.c.Git().WorkingTree.MergeFileForFiles(strategy, oursFilepath, baseFilepath, theirsFilepath)
+}
+
+func (self *WorkingTreeHelper) mergeFileWithObjectIDs(filepath, strategy string) (string, error) {
+	baseID, err := self.c.Git().WorkingTree.ObjectIDAtStage(filepath, 1)
+	if err != nil {
+		return "", err
+	}
+
+	oursID, err := self.c.Git().WorkingTree.ObjectIDAtStage(filepath, 2)
+	if err != nil {
+		return "", err
+	}
+
+	theirsID, err := self.c.Git().WorkingTree.ObjectIDAtStage(filepath, 3)
+	if err != nil {
+		return "", err
+	}
+
+	return self.c.Git().WorkingTree.MergeFileForObjectIDs(strategy, oursID, baseID, theirsID)
+}
+
+func (self *WorkingTreeHelper) CreateMergeConflictMenu(selectedFilepaths []string) error {
+	onMergeStrategySelected := func(strategy string) error {
+		for _, filepath := range selectedFilepaths {
+			output, err := self.mergeFile(filepath, strategy)
+			if err != nil {
+				return err
+			}
+
+			if err = os.WriteFile(filepath, []byte(output), 0o644); err != nil {
+				return err
+			}
+		}
+
+		err := self.c.Git().WorkingTree.StageFiles(selectedFilepaths, nil)
+		self.c.Refresh(types.RefreshOptions{Mode: types.SYNC, Scope: []types.RefreshableView{types.FILES}})
+		return err
+	}
+
+	cmdColor := style.FgBlue
+	return self.c.Menu(types.CreateMenuOptions{
+		Title: self.c.Tr.MergeConflictOptionsTitle,
+		Items: []*types.MenuItem{
+			{
+				LabelColumns: []string{
+					self.c.Tr.UseCurrentChanges,
+					cmdColor.Sprint("git merge-file --ours"),
+				},
+				OnPress: func() error {
+					return onMergeStrategySelected("--ours")
+				},
+				Key: 'c',
+			},
+			{
+				LabelColumns: []string{
+					self.c.Tr.UseIncomingChanges,
+					cmdColor.Sprint("git merge-file --theirs"),
+				},
+				OnPress: func() error {
+					return onMergeStrategySelected("--theirs")
+				},
+				Key: 'i',
+			},
+			{
+				LabelColumns: []string{
+					self.c.Tr.UseBothChanges,
+					cmdColor.Sprint("git merge-file --union"),
+				},
+				OnPress: func() error {
+					return onMergeStrategySelected("--union")
+				},
+				Key: 'b',
+			},
+			{
+				LabelColumns: []string{
+					self.c.Tr.OpenMergeTool,
+					cmdColor.Sprint("git mergetool"),
+				},
+				OnPress: self.OpenMergeTool,
+				Key:     'm',
+			},
+		},
+	})
+}

pkg/gui/controllers/merge_conflicts_controller.go

@@ -112,10 +112,11 @@ func (self *MergeConflictsController) GetKeybindings(opts types.KeybindingsOpts)
 			Tag:         "navigation",
 		},
 		{
-			Key:             opts.GetKey(opts.Config.Files.OpenMergeTool),
-			Handler:         self.c.Helpers().WorkingTree.OpenMergeTool,
-			Description:     self.c.Tr.OpenMergeTool,
-			Tooltip:         self.c.Tr.OpenMergeToolTooltip,
+			Key:             opts.GetKey(opts.Config.Files.OpenMergeOptions),
+			Handler:         self.openMergeConflictMenu,
+			Description:     self.c.Tr.ViewMergeConflictOptions,
+			Tooltip:         self.c.Tr.ViewMergeConflictOptionsTooltip,
+			OpensMenu:       true,
 			DisplayOnScreen: true,
 		},
 		{
@@ -320,6 +321,11 @@ func (self *MergeConflictsController) onLastConflictResolved() {
 	self.c.Refresh(types.RefreshOptions{Mode: types.ASYNC, Scope: []types.RefreshableView{types.FILES}})
 }
 
+func (self *MergeConflictsController) openMergeConflictMenu() error {
+	filepath := self.context().GetState().GetPath()
+	return self.c.Helpers().WorkingTree.CreateMergeConflictMenu([]string{filepath})
+}
+
 func (self *MergeConflictsController) withRenderAndFocus(f func() error) func() error {
 	return self.withLock(func() error {
 		if err := f(); err != nil {

pkg/i18n/english.go

@@ -63,7 +63,6 @@ type TranslationSet struct {
 	ToggleTreeViewTooltip                 string
 	OpenDiffTool                          string
 	OpenMergeTool                         string
-	OpenMergeToolTooltip                  string
 	Refresh                               string
 	RefreshTooltip                        string
 	Push                                  string
@@ -898,6 +897,13 @@ type TranslationSet struct {
 	BreakingChangesTitle                     string
 	BreakingChangesMessage                   string
 	BreakingChangesByVersion                 map[string]string
+	ViewMergeConflictOptions                 string
+	ViewMergeConflictOptionsTooltip          string
+	NoFilesWithMergeConflicts                string
+	MergeConflictOptionsTitle                string
+	UseCurrentChanges                        string
+	UseIncomingChanges                       string
+	UseBothChanges                           string
 }
 
 type Bisect struct {
@@ -1136,7 +1142,6 @@ func EnglishTranslationSet() *TranslationSet {
 		ToggleTreeViewTooltip:                "Toggle file view between flat and tree layout. Flat layout shows all file paths in a single list, tree layout groups files by directory.\n\nThe default can be changed in the config file with the key 'gui.showFileTree'.",
 		OpenDiffTool:                         "Open external diff tool (git difftool)",
 		OpenMergeTool:                        "Open external merge tool",
-		OpenMergeToolTooltip:                 "Run `git mergetool`.",
 		Refresh:                              "Refresh",
 		RefreshTooltip:                       "Refresh the git state (i.e. run `git status`, `git branch`, etc in background to update the contents of panels). This does not run `git fetch`.",
 		Push:                                 "Push",
@@ -1970,6 +1975,13 @@ func EnglishTranslationSet() *TranslationSet {
 		CustomCommands:                           "Custom commands",
 		NoApplicableCommandsInThisContext:        "(No applicable commands in this context)",
 		SelectCommitsOfCurrentBranch:             "Select commits of current branch",
+		ViewMergeConflictOptions:                 "View merge conflict options",
+		ViewMergeConflictOptionsTooltip:          "View options for resolving merge conflicts.",
+		NoFilesWithMergeConflicts:                "There are no files with merge conflicts.",
+		MergeConflictOptionsTitle:                "Resolve merge conflicts",
+		UseCurrentChanges:                        "Use current changes",
+		UseIncomingChanges:                       "Use incoming changes",
+		UseBothChanges:                           "Use both",
 
 		Actions: Actions{
 			// TODO: combine this with the original keybinding descriptions (those are all in lowercase atm)

pkg/integration/tests/conflicts/merge_file_both.go

@@ -0,0 +1,77 @@
+package conflicts
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+	"github.com/jesseduffield/lazygit/pkg/integration/tests/shared"
+)
+
+func testDataBoth() (original, current, incoming, final string) {
+	original = `
+1
+2
+3
+4
+5
+6
+`
+	current = `
+1a
+2
+3
+4
+5a
+6
+`
+	incoming = `
+1
+2
+3b
+4
+5b
+6
+`
+	final = `
+1a
+2
+3b
+4
+5a
+5b
+6
+`
+	return original, current, incoming, final
+}
+
+var MergeFileBoth = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Conflicting file can be resolved to 'union' (both changes) version via merge-file",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		original, current, incoming, _ := testDataBoth()
+		shared.CreateMergeConflictFileForMergeFileTests(shell, original, current, incoming)
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		_, _, _, expected := testDataBoth()
+
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				Contains("file").IsSelected(),
+			)
+
+		t.GlobalPress(keys.Files.OpenMergeOptions)
+
+		t.ExpectPopup().Menu().
+			Title(Equals("Resolve merge conflicts")).
+			Select(Contains("Use both")). // merge-file --union
+			Confirm()
+
+		t.Common().ContinueOnConflictsResolved("merge")
+
+		t.Views().Files().IsEmpty()
+
+		t.FileSystem().FileContent("file", Equals(expected))
+	},
+})

pkg/integration/tests/conflicts/merge_file_current.go

@@ -0,0 +1,76 @@
+package conflicts
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+	"github.com/jesseduffield/lazygit/pkg/integration/tests/shared"
+)
+
+func testDataCurrent() (original, current, incoming, final string) {
+	original = `
+1
+2
+3
+4
+5
+6
+`
+	current = `
+1
+2
+3
+4
+5a
+6
+`
+	incoming = `
+1b
+2
+3
+4
+5b
+6
+`
+	final = `
+1b
+2
+3
+4
+5a
+6
+`
+	return original, current, incoming, final
+}
+
+var MergeFileCurrent = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Conflicting file can be resolved to 'ours' (current changes) version via merge-file",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		original, current, incoming, _ := testDataCurrent()
+		shared.CreateMergeConflictFileForMergeFileTests(shell, original, current, incoming)
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		_, _, _, expected := testDataCurrent()
+
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				Contains("file").IsSelected(),
+			)
+
+		t.GlobalPress(keys.Files.OpenMergeOptions)
+
+		t.ExpectPopup().Menu().
+			Title(Equals("Resolve merge conflicts")).
+			Select(Contains("Use current changes")). // merge-file --ours
+			Confirm()
+
+		t.Common().ContinueOnConflictsResolved("merge")
+
+		t.Views().Files().IsEmpty()
+
+		t.FileSystem().FileContent("file", Equals(expected))
+	},
+})

pkg/integration/tests/conflicts/merge_file_incoming.go

@@ -0,0 +1,76 @@
+package conflicts
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+	"github.com/jesseduffield/lazygit/pkg/integration/tests/shared"
+)
+
+func testDataIncoming() (original, current, incoming, final string) {
+	original = `
+1
+2
+3
+4
+5
+6
+`
+	current = `
+1a
+2
+3
+4
+5a
+6
+`
+	incoming = `
+1
+2
+3
+4
+5b
+6
+`
+	final = `
+1a
+2
+3
+4
+5b
+6
+`
+	return original, current, incoming, final
+}
+
+var MergeFileIncoming = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Conflicting file can be resolved to 'theirs' (incoming changes) version via merge-file",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		original, current, incoming, _ := testDataIncoming()
+		shared.CreateMergeConflictFileForMergeFileTests(shell, original, current, incoming)
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		_, _, _, expected := testDataIncoming()
+
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				Contains("file").IsSelected(),
+			)
+
+		t.GlobalPress(keys.Files.OpenMergeOptions)
+
+		t.ExpectPopup().Menu().
+			Title(Equals("Resolve merge conflicts")).
+			Select(Contains("Use incoming changes")). // merge-file --theirs
+			Confirm()
+
+		t.Common().ContinueOnConflictsResolved("merge")
+
+		t.Views().Files().IsEmpty()
+
+		t.FileSystem().FileContent("file", Equals(expected))
+	},
+})

pkg/integration/tests/shared/conflicts.go

@@ -157,3 +157,20 @@ var CreateMergeConflictFileMultiple = func(shell *Shell) {
 
 	shell.RunCommandExpectError([]string{"git", "merge", "--no-edit", "second-change-branch"})
 }
+
+var CreateMergeConflictFileForMergeFileTests = func(shell *Shell, originalFileContent string, currentChangeFileContent string, incomingChangeFileContent string) {
+	shell.
+		NewBranch("original-branch").
+		EmptyCommit("one").
+		CreateFileAndAdd("file", originalFileContent).
+		Commit("original").
+		NewBranch("current-change-branch").
+		UpdateFileAndAdd("file", currentChangeFileContent).
+		Commit("first change").
+		Checkout("original-branch").
+		NewBranch("incoming-change-branch").
+		UpdateFileAndAdd("file", incomingChangeFileContent).
+		Commit("second change").
+		Checkout("current-change-branch").
+		RunCommandExpectError([]string{"git", "merge", "--no-edit", "incoming-change-branch"})
+}

pkg/integration/tests/test_list.go

@@ -150,6 +150,9 @@ var tests = []*components.IntegrationTest{
 	config.NegativeRefspec,
 	config.RemoteNamedStar,
 	conflicts.Filter,
+	conflicts.MergeFileBoth,
+	conflicts.MergeFileCurrent,
+	conflicts.MergeFileIncoming,
 	conflicts.ResolveExternally,
 	conflicts.ResolveMultipleFiles,
 	conflicts.ResolveNoAutoStage,

schema/config.json

@@ -1115,7 +1115,7 @@
           "type": "string",
           "default": "`"
         },
-        "openMergeTool": {
+        "openMergeOptions": {
           "type": "string",
           "default": "M"
         },