Add merge menu with conflict resolver (#4889)

Implements #2026. I also
tried to address issues mentioned in the
#3477 PR.

Previously, pressing `M` opened an external merge tool. Now it opens a
merge options menu that allows selecting all conflicts in chosen files
as **ours** (HEAD), **theirs** (incoming), or **union** (both), while
still providing access to the external merge tool.

This uses [git-merge-file](https://git-scm.com/docs/git-merge-file) for
a 3-way merge with the `--ours`, `--theirs`, and `--union` flags. This
approach avoids the issue mentioned in
#1608 (reply in thread),
and correctly applies the chosen conflict resolutions while preserving
changes from other branches. The command is executed with `--object-id`,
which requires object IDs obtained via `rev-parse`, instead of relying
on the standard version that works with full saved files.

Author: stefanhaller

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 |