introduce --merge to bring up merge editor (for #5770)

src/vs/code/electron-main/app.ts

@@ -1012,6 +1012,7 @@ export class CodeApplication extends Disposable {
 			cli: args,
 			forceNewWindow: args['new-window'] || (!hasCliArgs && args['unity-launch']),
 			diffMode: args.diff,
+			mergeMode: args.merge,
 			noRecentEntry,
 			waitMarkerFileURI,
 			gotoLineMode: args.goto,

src/vs/platform/environment/common/argv.ts

@@ -18,6 +18,7 @@ export interface NativeParsedArgs {
 	wait?: boolean;
 	waitMarkerFilePath?: string;
 	diff?: boolean;
+	merge?: boolean;
 	add?: boolean;
 	goto?: boolean;
 	'new-window'?: boolean;

src/vs/platform/environment/node/argv.ts

@@ -41,6 +41,7 @@ type OptionTypeName<T> =
 
 export const OPTIONS: OptionDescriptions<Required<NativeParsedArgs>> = {
 	'diff': { type: 'boolean', cat: 'o', alias: 'd', args: ['file', 'file'], description: localize('diff', "Compare two files with each other.") },
+	'merge': { type: 'boolean', cat: 'o', alias: 'm', args: ['path1', 'path2', 'base', 'result'], description: localize('merge', "Perform a three-way merge by providing paths for two modified versions of a file, the common origin of both modified versions and the output file to save merge results.") },
 	'add': { type: 'boolean', cat: 'o', alias: 'a', args: 'folder', description: localize('add', "Add folder(s) to the last active window.") },
 	'goto': { type: 'boolean', cat: 'o', alias: 'g', args: 'file:line[:character]', description: localize('goto', "Open a file at the path on the specified line and character position.") },
 	'new-window': { type: 'boolean', cat: 'o', alias: 'n', description: localize('newWindow', "Force to open a new window.") },

src/vs/platform/launch/electron-main/launchMainService.ts

@@ -190,6 +190,7 @@ export class LaunchMainService implements ILaunchMainService {
 				preferNewWindow: !args['reuse-window'] && !args.wait,
 				forceReuseWindow: args['reuse-window'],
 				diffMode: args.diff,
+				mergeMode: args.merge,
 				addMode: args.add,
 				noRecentEntry: !!args['skip-add-to-recently-opened'],
 				gotoLineMode: args.goto

src/vs/platform/native/electron-main/nativeHostMainService.ts

@@ -154,6 +154,7 @@ export class NativeHostMainService extends Disposable implements INativeHostMain
 				forceReuseWindow: options.forceReuseWindow,
 				preferNewWindow: options.preferNewWindow,
 				diffMode: options.diffMode,
+				mergeMode: options.mergeMode,
 				addMode: options.addMode,
 				gotoLineMode: options.gotoLineMode,
 				noRecentEntry: options.noRecentEntry,

src/vs/platform/window/common/window.ts

@@ -52,6 +52,7 @@ export interface IOpenWindowOptions extends IBaseOpenWindowsOptions {
 	readonly addMode?: boolean;
 
 	readonly diffMode?: boolean;
+	readonly mergeMode?: boolean;
 	readonly gotoLineMode?: boolean;
 
 	readonly waitMarkerFileURI?: URI;
@@ -240,6 +241,7 @@ interface IPathsToWaitForData {
 export interface IOpenFileRequest {
 	readonly filesToOpenOrCreate?: IPathData[];
 	readonly filesToDiff?: IPathData[];
+	readonly filesToMerge?: IPathData[];
 }
 
 /**
@@ -270,6 +272,7 @@ export interface IWindowConfiguration {
 
 	filesToOpenOrCreate?: IPath[];
 	filesToDiff?: IPath[];
+	filesToMerge?: IPath[];
 }
 
 export interface IOSConfiguration {

src/vs/platform/windows/electron-main/window.ts

@@ -899,6 +899,7 @@ export class CodeWindow extends Disposable implements ICodeWindow {
 		// Delete some properties we do not want during reload
 		delete configuration.filesToOpenOrCreate;
 		delete configuration.filesToDiff;
+		delete configuration.filesToMerge;
 		delete configuration.filesToWait;
 
 		// Some configuration things get inherited if the window is being reloaded and we are

src/vs/platform/windows/electron-main/windows.ts

@@ -85,6 +85,7 @@ export interface IOpenConfiguration extends IBaseOpenConfiguration {
 	readonly forceReuseWindow?: boolean;
 	readonly forceEmpty?: boolean;
 	readonly diffMode?: boolean;
+	readonly mergeMode?: boolean;
 	addMode?: boolean;
 	readonly gotoLineMode?: boolean;
 	readonly initialStartup?: boolean;

src/vs/platform/windows/electron-main/windowsMainService.ts

@@ -118,6 +118,8 @@ interface IFilesToOpen {
 
 	filesToOpenOrCreate: IPath[];
 	filesToDiff: IPath[];
+	filesToMerge: IPath[];
+
 	filesToWait?: IPathsToWaitFor;
 }
 
@@ -296,7 +298,7 @@ export class WindowsMainService extends Disposable implements IWindowsMainServic
 				workspacesToOpen.push(path);
 			} else if (path.fileUri) {
 				if (!filesToOpen) {
-					filesToOpen = { filesToOpenOrCreate: [], filesToDiff: [], remoteAuthority: path.remoteAuthority };
+					filesToOpen = { filesToOpenOrCreate: [], filesToDiff: [], filesToMerge: [], remoteAuthority: path.remoteAuthority };
 				}
 				filesToOpen.filesToOpenOrCreate.push(path);
 			} else if (path.backupPath) {
@@ -312,9 +314,16 @@ export class WindowsMainService extends Disposable implements IWindowsMainServic
 			filesToOpen.filesToOpenOrCreate = [];
 		}
 
+		// When run with --merge, take the first 4 files to open as files to merge
+		if (openConfig.mergeMode && filesToOpen && filesToOpen.filesToOpenOrCreate.length === 4) {
+			filesToOpen.filesToMerge = filesToOpen.filesToOpenOrCreate.slice(0, 4);
+			filesToOpen.filesToOpenOrCreate = [];
+			filesToOpen.filesToDiff = [];
+		}
+
 		// When run with --wait, make sure we keep the paths to wait for
 		if (filesToOpen && openConfig.waitMarkerFileURI) {
-			filesToOpen.filesToWait = { paths: [...filesToOpen.filesToDiff, ...filesToOpen.filesToOpenOrCreate], waitMarkerFileUri: openConfig.waitMarkerFileURI };
+			filesToOpen.filesToWait = { paths: [...filesToOpen.filesToDiff, filesToOpen.filesToMerge[3] /* [3] is the resulting merge file */, ...filesToOpen.filesToOpenOrCreate], waitMarkerFileUri: openConfig.waitMarkerFileURI };
 		}
 
 		// These are windows to restore because of hot-exit or from previous session (only performed once on startup!)
@@ -384,9 +393,10 @@ export class WindowsMainService extends Disposable implements IWindowsMainServic
 		}
 
 		// Remember in recent document list (unless this opens for extension development)
-		// Also do not add paths when files are opened for diffing, only if opened individually
+		// Also do not add paths when files are opened for diffing or merging, only if opened individually
 		const isDiff = filesToOpen && filesToOpen.filesToDiff.length > 0;
-		if (!usedWindows.some(window => window.isExtensionDevelopmentHost) && !isDiff && !openConfig.noRecentEntry) {
+		const isMerge = filesToOpen && filesToOpen.filesToMerge.length > 0;
+		if (!usedWindows.some(window => window.isExtensionDevelopmentHost) && !isDiff && !isMerge && !openConfig.noRecentEntry) {
 			const recents: IRecent[] = [];
 			for (const pathToOpen of pathsToOpen) {
 				if (isWorkspacePathToOpen(pathToOpen) && !pathToOpen.transient /* never add transient workspaces to history */) {
@@ -461,13 +471,13 @@ export class WindowsMainService extends Disposable implements IWindowsMainServic
 			}
 		}
 
-		// Handle files to open/diff or to create when we dont open a folder and we do not restore any
+		// Handle files to open/diff/merge or to create when we dont open a folder and we do not restore any
 		// folder/untitled from hot-exit by trying to open them in the window that fits best
 		const potentialNewWindowsCount = foldersToOpen.length + workspacesToOpen.length + emptyToRestore.length;
 		if (filesToOpen && potentialNewWindowsCount === 0) {
 
 			// Find suitable window or folder path to open files in
-			const fileToCheck = filesToOpen.filesToOpenOrCreate[0] || filesToOpen.filesToDiff[0];
+			const fileToCheck = filesToOpen.filesToOpenOrCreate[0] || filesToOpen.filesToDiff[0] || filesToOpen.filesToMerge[3] /* [3] is the resulting merge file */;
 
 			// only look at the windows with correct authority
 			const windows = this.getWindows().filter(window => filesToOpen && isEqualAuthority(window.remoteAuthority, filesToOpen.remoteAuthority));
@@ -625,6 +635,7 @@ export class WindowsMainService extends Disposable implements IWindowsMainServic
 		const params: INativeOpenFileRequest = {
 			filesToOpenOrCreate: filesToOpen?.filesToOpenOrCreate,
 			filesToDiff: filesToOpen?.filesToDiff,
+			filesToMerge: filesToOpen?.filesToMerge,
 			filesToWait: filesToOpen?.filesToWait,
 			termProgram: configuration?.userEnv?.['TERM_PROGRAM']
 		};
@@ -792,7 +803,12 @@ export class WindowsMainService extends Disposable implements IWindowsMainServic
 			ignoreFileNotFound: true,
 			gotoLineMode: cli.goto,
 			remoteAuthority: cli.remote || undefined,
-			forceOpenWorkspaceAsFile: cli.diff && cli._.length === 2 // special case diff mode to force open workspace as file (https://github.com/microsoft/vscode/issues/149731)
+			forceOpenWorkspaceAsFile:
+				// special case diff / merge mode to force open
+				// workspace as file
+				// https://github.com/microsoft/vscode/issues/149731
+				cli.diff && cli._.length === 2 ||
+				cli.merge && cli._.length === 4
 		};
 
 		// folder uris
@@ -1323,6 +1339,7 @@ export class WindowsMainService extends Disposable implements IWindowsMainServic
 
 			filesToOpenOrCreate: options.filesToOpen?.filesToOpenOrCreate,
 			filesToDiff: options.filesToOpen?.filesToDiff,
+			filesToMerge: options.filesToOpen?.filesToMerge,
 			filesToWait: options.filesToOpen?.filesToWait,
 
 			logLevel: this.logService.getLevel(),

src/vs/server/node/server.cli.ts

@@ -59,6 +59,7 @@ const isSupportedForPipe = (optionId: keyof RemoteParsedArgs) => {
 		case 'file-uri':
 		case 'add':
 		case 'diff':
+		case 'merge':
 		case 'wait':
 		case 'goto':
 		case 'reuse-window':
@@ -297,6 +298,7 @@ export function main(desc: ProductDescription, args: string[]): void {
 			fileURIs,
 			folderURIs,
 			diffMode: parsedArgs.diff,
+			mergeMode: parsedArgs.merge,
 			addMode: parsedArgs.add,
 			gotoLineMode: parsedArgs.goto,
 			forceReuseWindow: parsedArgs['reuse-window'],

src/vs/workbench/api/node/extHostCLIServer.ts

@@ -18,6 +18,7 @@ export interface OpenCommandPipeArgs {
 	folderURIs?: string[];
 	forceNewWindow?: boolean;
 	diffMode?: boolean;
+	mergeMode?: boolean;
 	addMode?: boolean;
 	gotoLineMode?: boolean;
 	forceReuseWindow?: boolean;
@@ -118,7 +119,7 @@ export class CLIServerBase {
 	}
 
 	private async open(data: OpenCommandPipeArgs): Promise<string> {
-		const { fileURIs, folderURIs, forceNewWindow, diffMode, addMode, forceReuseWindow, gotoLineMode, waitMarkerFilePath, remoteAuthority } = data;
+		const { fileURIs, folderURIs, forceNewWindow, diffMode, mergeMode, addMode, forceReuseWindow, gotoLineMode, waitMarkerFilePath, remoteAuthority } = data;
 		const urisToOpen: IWindowOpenable[] = [];
 		if (Array.isArray(folderURIs)) {
 			for (const s of folderURIs) {
@@ -144,7 +145,7 @@ export class CLIServerBase {
 		}
 		const waitMarkerFileURI = waitMarkerFilePath ? URI.file(waitMarkerFilePath) : undefined;
 		const preferNewWindow = !forceReuseWindow && !waitMarkerFileURI && !addMode;
-		const windowOpenArgs: IOpenWindowOptions = { forceNewWindow, diffMode, addMode, gotoLineMode, forceReuseWindow, preferNewWindow, waitMarkerFileURI, remoteAuthority };
+		const windowOpenArgs: IOpenWindowOptions = { forceNewWindow, diffMode, mergeMode, addMode, gotoLineMode, forceReuseWindow, preferNewWindow, waitMarkerFileURI, remoteAuthority };
 		this._commands.executeCommand('_remoteCLI.windowOpen', urisToOpen, windowOpenArgs);
 
 		return '';

src/vs/workbench/browser/layout.ts

@@ -9,7 +9,7 @@ import { EventType, addDisposableListener, getClientArea, Dimension, position, s
 import { onDidChangeFullscreen, isFullscreen } from 'vs/base/browser/browser';
 import { IWorkingCopyBackupService } from 'vs/workbench/services/workingCopy/common/workingCopyBackup';
 import { isWindows, isLinux, isMacintosh, isWeb, isNative, isIOS } from 'vs/base/common/platform';
-import { IUntypedEditorInput, pathsToEditors } from 'vs/workbench/common/editor';
+import { isResourceEditorInput, IUntypedEditorInput, pathsToEditors } from 'vs/workbench/common/editor';
 import { SideBySideEditorInput } from 'vs/workbench/common/editor/sideBySideEditorInput';
 import { SidebarPart } from 'vs/workbench/browser/parts/sidebar/sidebarPart';
 import { PanelPart } from 'vs/workbench/browser/parts/panel/panelPart';
@@ -75,7 +75,7 @@ interface IWorkbenchLayoutWindowInitializationState {
 	};
 	editor: {
 		restoreEditors: boolean;
-		editorsToOpen: Promise<IUntypedEditorInput[]> | IUntypedEditorInput[];
+		editorsToOpen: Promise<IUntypedEditorInput[]>;
 	};
 }
 
@@ -98,6 +98,7 @@ enum WorkbenchLayoutClasses {
 interface IInitialFilesToOpen {
 	filesToOpenOrCreate?: IPath[];
 	filesToDiff?: IPath[];
+	filesToMerge?: IPath[];
 }
 
 export abstract class Layout extends Disposable implements IWorkbenchLayoutService {
@@ -278,7 +279,7 @@ export abstract class Layout extends Disposable implements IWorkbenchLayoutServi
 		this._register(this.hostService.onDidChangeFocus(e => this.onWindowFocusChanged(e)));
 	}
 
-	private onMenubarToggled(visible: boolean) {
+	private onMenubarToggled(visible: boolean): void {
 		if (visible !== this.windowState.runtime.menuBar.toggled) {
 			this.windowState.runtime.menuBar.toggled = visible;
 
@@ -565,26 +566,33 @@ export abstract class Layout extends Disposable implements IWorkbenchLayoutServi
 		return this.windowState.initialization.editor.restoreEditors;
 	}
 
-	private resolveEditorsToOpen(fileService: IFileService, initialFilesToOpen: IInitialFilesToOpen | undefined): Promise<IUntypedEditorInput[]> | IUntypedEditorInput[] {
-
-		// Files to open, diff or create
+	private async resolveEditorsToOpen(fileService: IFileService, initialFilesToOpen: IInitialFilesToOpen | undefined): Promise<IUntypedEditorInput[]> {
 		if (initialFilesToOpen) {
 
-			// Files to diff is exclusive
-			return pathsToEditors(initialFilesToOpen.filesToDiff, fileService).then(filesToDiff => {
-				if (filesToDiff.length === 2) {
-					const diffEditorInput: IUntypedEditorInput[] = [{
-						original: { resource: filesToDiff[0].resource },
-						modified: { resource: filesToDiff[1].resource },
-						options: { pinned: true }
-					}];
+			// Merge editor
+			const filesToMerge = await pathsToEditors(initialFilesToOpen.filesToMerge, fileService);
+			if (filesToMerge.length === 4 && isResourceEditorInput(filesToMerge[0]) && isResourceEditorInput(filesToMerge[1]) && isResourceEditorInput(filesToMerge[2]) && isResourceEditorInput(filesToMerge[3])) {
+				return [{
+					input1: { resource: filesToMerge[0].resource },
+					input2: { resource: filesToMerge[1].resource },
+					base: { resource: filesToMerge[2].resource },
+					result: { resource: filesToMerge[3].resource },
+					options: { pinned: true, override: 'mergeEditor.Input' } // TODO@bpasero remove the override once the resolver is ready
+				}];
+			}
 
-					return diffEditorInput;
-				}
+			// Diff editor
+			const filesToDiff = await pathsToEditors(initialFilesToOpen.filesToDiff, fileService);
+			if (filesToDiff.length === 2) {
+				return [{
+					original: { resource: filesToDiff[0].resource },
+					modified: { resource: filesToDiff[1].resource },
+					options: { pinned: true }
+				}];
+			}
 
-				// Otherwise: Open/Create files
-				return pathsToEditors(initialFilesToOpen.filesToOpenOrCreate, fileService);
-			});
+			// Normal editor
+			return pathsToEditors(initialFilesToOpen.filesToOpenOrCreate, fileService);
 		}
 
 		// Empty workbench configured to open untitled file if empty
@@ -593,13 +601,12 @@ export abstract class Layout extends Disposable implements IWorkbenchLayoutServi
 				return []; // do not open any empty untitled file if we restored groups/editors from previous session
 			}
 
-			return this.workingCopyBackupService.hasBackups().then(hasBackups => {
-				if (hasBackups) {
-					return []; // do not open any empty untitled file if we have backups to restore
-				}
+			const hasBackups = await this.workingCopyBackupService.hasBackups();
+			if (hasBackups) {
+				return []; // do not open any empty untitled file if we have backups to restore
+			}
 
-				return [{ resource: undefined }]; // open empty untitled file
-			});
+			return [{ resource: undefined }]; // open empty untitled file
 		}
 
 		return [];
@@ -638,10 +645,10 @@ export abstract class Layout extends Disposable implements IWorkbenchLayoutServi
 			};
 		}
 
-		// Then check for files to open, create or diff from main side
-		const { filesToOpenOrCreate, filesToDiff } = this.environmentService;
-		if (filesToOpenOrCreate || filesToDiff) {
-			return { filesToOpenOrCreate, filesToDiff };
+		// Then check for files to open, create or diff/merge from main side
+		const { filesToOpenOrCreate, filesToDiff, filesToMerge } = this.environmentService;
+		if (filesToOpenOrCreate || filesToDiff || filesToMerge) {
+			return { filesToOpenOrCreate, filesToDiff, filesToMerge };
 		}
 
 		return undefined;
@@ -681,12 +688,7 @@ export abstract class Layout extends Disposable implements IWorkbenchLayoutServi
 			// signaling that layout is restored, but we do
 			// not need to await the editors from having
 			// fully loaded.
-			let editors: IUntypedEditorInput[];
-			if (Array.isArray(this.windowState.initialization.editor.editorsToOpen)) {
-				editors = this.windowState.initialization.editor.editorsToOpen;
-			} else {
-				editors = await this.windowState.initialization.editor.editorsToOpen;
-			}
+			const editors = await this.windowState.initialization.editor.editorsToOpen;
 
 			let openEditorsPromise: Promise<unknown> | undefined = undefined;
 			if (editors.length) {