src/vs/workbench/contrib/mergeEditor/browser/model/mergeEditorModel.ts/MergeEditorModel/setLanguageId
class MergeEditorModel:	public setLanguageId(languageId: string): void {
		const language = this.languageService.createById(languageId);
		this.modelService.setMode(this.base, language);
		this.modelService.setMode(this.input1, language);
		this.modelService.setMode(this.input2, language);
		this.modelService.setMode(this.result, language);
	}