Implements first iteration of multi diff editors.

Co-authored-by: Ladislau Szomoru <3372902+lszomoru@users.noreply.github.com>

extensions/git/src/commands.ts

@@ -3426,6 +3426,54 @@ export class CommandCenter {
 		};
 	}
 
+	@command('git.timeline.openCommit', { repository: false })
+	async timelineOpenCommit(item: TimelineItem, uri: Uri | undefined, _source: string) {
+		console.log('timelineOpenCommit', item);
+		if (!GitTimelineItem.is(item)) {
+			return;
+		}
+
+		const cmd = await this._resolveTimelineOpenCommitCommand(
+			item, uri,
+			{
+				preserveFocus: true,
+				preview: true,
+				viewColumn: ViewColumn.Active
+			},
+		);
+		if (cmd === undefined) {
+			return undefined;
+		}
+
+		return commands.executeCommand(cmd.command, ...(cmd.arguments ?? []));
+	}
+
+	private async _resolveTimelineOpenCommitCommand(item: TimelineItem, uri: Uri | undefined, options?: TextDocumentShowOptions): Promise<Command | undefined> {
+		if (uri === undefined || uri === null || !GitTimelineItem.is(item)) {
+			return undefined;
+		}
+
+		const repository = await this.model.getRepository(uri.fsPath);
+		if (!repository) {
+			return undefined;
+		}
+
+		const commit = await repository.getCommit(item.ref);
+		const commitFiles = await repository.getCommitFiles(item.ref);
+
+		const args: [Uri, Uri | undefined, Uri | undefined][] = [];
+		for (const commitFile of commitFiles) {
+			const commitFileUri = Uri.file(path.join(repository.root, commitFile));
+			args.push([commitFileUri, toGitUri(commitFileUri, item.previousRef), toGitUri(commitFileUri, item.ref)]);
+		}
+
+		return {
+			command: 'vscode.changes',
+			title: l10n.t('Open Commit'),
+			arguments: [`${item.shortRef} - ${commit.message}`, args, options]
+		};
+	}
+
 	@command('git.timeline.copyCommitId', { repository: false })
 	async timelineCopyCommitId(item: TimelineItem, _uri: Uri | undefined, _source: string) {
 		if (!GitTimelineItem.is(item)) {
@@ -3603,6 +3651,26 @@ export class CommandCenter {
 		repository.generateCommitMessageCancel();
 	}
 
+	@command('git.viewChanges', { repository: true })
+	viewChanges(repository: Repository): void {
+		this._viewChanges('Changes', repository.workingTreeGroup.resourceStates);
+	}
+
+	@command('git.viewStagedChanges', { repository: true })
+	viewStagedChanges(repository: Repository): void {
+		this._viewChanges('Staged Changes', repository.indexGroup.resourceStates);
+	}
+
+	private _viewChanges(title: string, resources: Resource[]): void {
+		const args: [Uri, Uri | undefined, Uri | undefined][] = [];
+
+		for (const resource of resources) {
+			args.push([resource.resourceUri, resource.leftUri, resource.rightUri]);
+		}
+
+		commands.executeCommand('vscode.changes', title, args);
+	}
+
 	private createCommand(id: string, key: string, method: Function, options: ScmCommandOptions): (...args: any[]) => any {
 		const result = (...args: any[]) => {
 			let result: Promise<any>;

extensions/git/src/git.ts

@@ -2552,6 +2552,11 @@ export class Repository {
 		return commits[0];
 	}
 
+	async getCommitFiles(ref: string): Promise<string[]> {
+		const result = await this.exec(['diff-tree', '--no-commit-id', '--name-only', '-r', ref]);
+		return result.stdout.split('\n').filter(l => !!l);
+	}
+
 	async getCommitCount(range: string): Promise<{ ahead: number; behind: number }> {
 		const result = await this.exec(['rev-list', '--count', '--left-right', range]);
 		const [ahead, behind] = result.stdout.trim().split('\t');

extensions/git/src/repository.ts

@@ -1658,6 +1658,10 @@ export class Repository implements Disposable {
 		return await this.repository.getCommit(ref);
 	}
 
+	async getCommitFiles(ref: string): Promise<string[]> {
+		return await this.repository.getCommitFiles(ref);
+	}
+
 	async getCommitCount(range: string): Promise<{ ahead: number; behind: number }> {
 		return await this.run(Operation.RevList, () => this.repository.getCommitCount(range));
 	}