src/vs/workbench/browser/parts/editor/editorGroupView.ts/EditorGroupView/openEditor
class EditorGroupView:	async openEditor(editor: EditorInput, options?: IEditorOptions): Promise<IEditorPane | undefined> {
		return this.doOpenEditor(editor, options, {
			// Allow to match on a side-by-side editor when same
			// editor is opened on both sides. In that case we
			// do not want to open a new editor but reuse that one.
			supportSideBySide: SideBySideEditor.BOTH
		});
	}