src/vs/workbench/browser/parts/editor/textDiffEditor.ts/TextDiffEditor/updateReadonly
class TextDiffEditor:	private updateReadonly(input: DiffEditorInput): void {
		const control = this.getControl();
		if (control) {
			control.updateOptions({
				readOnly: input.modifiedInput.hasCapability(EditorInputCapabilities.Readonly),
				originalEditable: !input.originalInput.hasCapability(EditorInputCapabilities.Readonly)
			});
		}
	}