/**
 * Environment variables that flatten every editor into one (#817, plan 6.7).
 *
 * Each of these is read once per process and applied everywhere, which is
 * exactly right for a server driving one editor and exactly wrong for a server
 * driving several: one value cannot describe two projects on two engine
 * versions, two hosts, or two config overlays. Every one of them now has a
 * per-project equivalent, and the env var stays the global default that wins.
 *
 * Winning is the part that has to be said out loud. A user who sets one of
 * these and then writes the per-project key gets the env var, silently, in
 * every session. So while more than one editor is registered, a set variable is
 * reported by name along with the sessions it flattens and the key that would
 * tell them apart. At one editor nothing here runs: there is nothing to
 * flatten and no message to print.
 */
export interface CollapsingEnvVar {
    /** The variable that is set. */
    variable: string;
    /** The per-project key that differentiates the sessions when it is unset. */
    configKey: string;
    /** What it decides, in the reader's terms. */
    decides: string;
}
/**
 * One line per set variable, naming the sessions it applies to.
 *
 * Returns nothing at one editor, which is what keeps a single-editor server's
 * startup output byte-identical.
 */
export declare function collapsingEnvWarnings(sessionNames: string[], env?: NodeJS.ProcessEnv): string[];