Add capability to specify auth from env var or stdin

This commit adds two new ways of specifying GitHub auth:

1. from the GITHUB_TOKEN environment variable
2. from standard input

This commit does not include any documentation changes and the
descriptions of new command line options will need to be tweaked.

src/util.test.ts

@@ -1,12 +1,13 @@
 import * as fs from "fs";
 import * as os from "os";
+import * as stream from "stream";
 
 import * as github from "@actions/github";
-import test from "ava";
+import test, { ExecutionContext } from "ava";
 import sinon from "sinon";
 
 import * as api from "./api-client";
-import { getRunnerLogger } from "./logging";
+import { getRunnerLogger, Logger } from "./logging";
 import { setupTests } from "./testing-utils";
 import * as util from "./util";
 
@@ -244,3 +245,62 @@ test("getGitHubVersion", async (t) => {
   });
   t.deepEqual({ type: util.GitHubVariant.DOTCOM }, v3);
 });
+
+test("getGitHubAuth", async (t) => {
+  const msgs: string[] = [];
+  const mockLogger = ({
+    warning: (msg: string) => msgs.push(msg),
+  } as unknown) as Logger;
+
+  // eslint-disable-next-line @typescript-eslint/no-floating-promises
+  t.throwsAsync(async () => util.getGitHubAuth(mockLogger, "abc", true));
+
+  process.env.GITHUB_TOKEN = "123";
+  t.is("123", await util.getGitHubAuth(mockLogger, undefined, undefined));
+  t.is(msgs.length, 0);
+  t.is("abc", await util.getGitHubAuth(mockLogger, "abc", undefined));
+  t.is(msgs.length, 1); // warning expected
+
+  msgs.length = 0;
+  await mockStdInForAuth(t, mockLogger, "def", "def");
+  await mockStdInForAuth(t, mockLogger, "def", "", "def");
+  await mockStdInForAuth(
+    t,
+    mockLogger,
+    "def",
+    "def\n some extra garbage",
+    "ghi"
+  );
+  await mockStdInForAuth(t, mockLogger, "defghi", "def", "ghi\n123");
+
+  await mockStdInForAuthExpectError(t, mockLogger, "");
+  await mockStdInForAuthExpectError(t, mockLogger, "", " ", "abc");
+  await mockStdInForAuthExpectError(
+    t,
+    mockLogger,
+    "  def\n some extra garbage",
+    "ghi"
+  );
+  t.is(msgs.length, 0);
+});
+
+async function mockStdInForAuth(
+  t: ExecutionContext<any>,
+  mockLogger: Logger,
+  expected: string,
+  ...text: string[]
+) {
+  const stdin = stream.Readable.from(text) as any;
+  t.is(expected, await util.getGitHubAuth(mockLogger, undefined, true, stdin));
+}
+
+async function mockStdInForAuthExpectError(
+  t: ExecutionContext<unknown>,
+  mockLogger: Logger,
+  ...text: string[]
+) {
+  const stdin = stream.Readable.from(text) as any;
+  await t.throwsAsync(async () =>
+    util.getGitHubAuth(mockLogger, undefined, true, stdin)
+  );
+}