git-notes.test: avoid fetching notes from GitHub

Every invocation used to fetch notes, multiple times, from
https://github.com/gitgitgadget/git. This is undesirable, as it is
actually totally irrelevant for the tests what is stored in that
repository, the tests only want to verify that `git fetch` was invoked.

Let's avoid network accesses unless necessary.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

tests/git-notes.test.ts

@@ -1,7 +1,7 @@
 import { expect, jest, test } from "@jest/globals";
 import { fileURLToPath } from "url";
 import { isDirectory } from "../lib/fs-util.js";
-import { git, revParse } from "../lib/git.js";
+import { emptyBlobName, git, revParse } from "../lib/git.js";
 import { GitNotes } from "../lib/git-notes.js";
 import { IPatchSeriesMetadata } from "../lib/patch-series-metadata.js";
 import { testCreateRepo } from "./test-lib.js";
@@ -23,6 +23,14 @@ test("set/get notes", async () => {
     expect(await git(["log", "-p", "refs/notes/gitgitgadget"], { workDir: repo.workDir })).toMatch(/\n\+hello$/);
 
     const gitURL = "https://github.com/gitgitgadget/git";
+    // avoid network calls during tests
+    const fakeRemote = `${repo.workDir}/.git/fake-remote`;
+    await git(["init", "--bare", fakeRemote]);
+    await git([`--git-dir=${fakeRemote}`, "notes", "--ref=gitgitgadget", "add", "-m", "{}", emptyBlobName]);
+    await git([`--git-dir=${fakeRemote}`, "notes", "--ref=mail-to-commit", "add", "-m", "1", emptyBlobName]);
+    await git([`--git-dir=${fakeRemote}`, "notes", "--ref=commit-to-mail", "add", "-m", "1", emptyBlobName]);
+    await git(["config", `url.${fakeRemote}.insteadof`, gitURL], { workDir: repo.workDir });
+
     const pullRequestURL = `${gitURL}/git/pull/1`;
     const metadata: IPatchSeriesMetadata = {
         baseCommit: "0123456789012345678901234567890123456789",