extensions/git/src/commands.ts/CommandCenter/resolveTimelineOpenDiffCommand
class CommandCenter:	resolveTimelineOpenDiffCommand(item: TimelineItem, uri: Uri | undefined, options?: TextDocumentShowOptions): Command | undefined {
		if (uri === undefined || uri === null || !GitTimelineItem.is(item)) {
			return undefined;
		}

		const basename = path.basename(uri.fsPath);

		let title;
		if ((item.previousRef === 'HEAD' || item.previousRef === '~') && item.ref === '') {
			title = l10n.t('{0} (Working Tree)', basename);
		}
		else if (item.previousRef === 'HEAD' && item.ref === '~') {
			title = l10n.t('{0} (Index)', basename);
		} else {
			title = l10n.t('{0} ({1}) ↔ {0} ({2})', basename, item.shortPreviousRef, item.shortRef);
		}

		return {
			command: 'vscode.diff',
			title: l10n.t('Open Comparison'),
			arguments: [toGitUri(uri, item.previousRef), item.ref === '' ? uri : toGitUri(uri, item.ref), title, options]
		};
	}