Infinite loop when computing completion items in ADD and COPY if the build stage shares the name with the image

[rcjsuen]

const lib = require("dockerfile-language-service")
const service = lib.DockerfileLanguageServiceFactory.createLanguageService();
service.computeCompletionItems("FROM a as a\nCOPY . . ", { line: 1, character: 9 });

This code will enter an infinite loop.

[rcjsuen]

Same thing happens for an ADD.

const lib = require("dockerfile-language-service")
const service = lib.DockerfileLanguageServiceFactory.createLanguageService();
service.computeCompletionItems("FROM a as a\nADD . . ", { line: 1, character: 8 });

[rcjsuen]

This is likely caused by rcjsuen/dockerfile-ast#100.