Avoid putting the github token in the global .netrc file (#670)

* Avoid putting the github token in the global `.netrc` file

* fix wording

src/github.ts

@@ -0,0 +1,179 @@
+import { Buffer } from "node:buffer";
+import * as core from "@actions/core";
+import { exec, getExecOutput } from "@actions/exec";
+import { context } from "@actions/github";
+import { commitChangesFromRepo } from "@changesets/ghcommit/git";
+import { setupOctokit, type Octokit } from "./octokit.ts";
+
+export type CommitMode = "git-cli" | "github-api";
+
+type GitOptions = {
+  cwd: string;
+  env?: Record<string, string>;
+};
+
+const push = async (branch: string, options: GitOptions) => {
+  await exec("git", ["push", "origin", `HEAD:${branch}`, "--force"], options);
+};
+
+const switchToMaybeExistingBranch = async (
+  branch: string,
+  options: GitOptions,
+) => {
+  let { stderr } = await getExecOutput("git", ["checkout", branch], {
+    ignoreReturnCode: true,
+    ...options,
+  });
+  let isCreatingBranch = !stderr
+    .toString()
+    .includes(`Switched to a new branch '${branch}'`);
+  if (isCreatingBranch) {
+    await exec("git", ["checkout", "-b", branch], options);
+  }
+};
+
+const reset = async (pathSpec: string, options: GitOptions) => {
+  await exec("git", ["reset", `--hard`, pathSpec], options);
+};
+
+const commitAll = async (message: string, options: GitOptions) => {
+  await exec("git", ["add", "."], options);
+  await exec("git", ["commit", "-m", message], options);
+};
+
+const checkIfClean = async (options: GitOptions): Promise<boolean> => {
+  const { stdout } = await getExecOutput(
+    "git",
+    ["status", "--porcelain"],
+    options,
+  );
+  return !stdout.length;
+};
+
+export class GitHub {
+  readonly #githubToken: string;
+  readonly octokit: Octokit;
+  readonly cwd: string;
+  readonly commitMode: CommitMode;
+
+  constructor(options: {
+    githubToken: string;
+    cwd: string;
+    commitMode?: CommitMode;
+  }) {
+    this.#githubToken = options.githubToken;
+    this.cwd = options.cwd;
+    this.commitMode = options.commitMode ?? "git-cli";
+    this.octokit = setupOctokit(options.githubToken);
+  }
+
+  getToken() {
+    return this.#githubToken;
+  }
+
+  #getCliAuthEnv(): Record<string, string> {
+    const basic = Buffer.from(`x-access-token:${this.#githubToken}`).toString(
+      "base64",
+    );
+    const serverUrl = (
+      context.serverUrl ??
+      process.env.GITHUB_SERVER_URL ??
+      "https://github.com"
+    ).replace(/\/+$/, "");
+    const gitConfigCount = Number(process.env.GIT_CONFIG_COUNT ?? 0);
+    if (!Number.isInteger(gitConfigCount) || gitConfigCount < 0) {
+      throw new Error(
+        `Invalid GIT_CONFIG_COUNT value: ${process.env.GIT_CONFIG_COUNT}`,
+      );
+    }
+    return {
+      GIT_CONFIG_COUNT: String(gitConfigCount + 1),
+      [`GIT_CONFIG_KEY_${gitConfigCount}`]: `http.${serverUrl}/.extraheader`,
+      [`GIT_CONFIG_VALUE_${gitConfigCount}`]: `AUTHORIZATION: basic ${basic}`,
+    };
+  }
+
+  async setupUser() {
+    if (this.commitMode === "github-api") {
+      return;
+    }
+    await exec("git", ["config", "user.name", `"github-actions[bot]"`], {
+      cwd: this.cwd,
+    });
+    await exec(
+      "git",
+      [
+        "config",
+        "user.email",
+        `"41898282+github-actions[bot]@users.noreply.github.com"`,
+      ],
+      {
+        cwd: this.cwd,
+      },
+    );
+  }
+
+  async pushTag(tag: string) {
+    if (this.commitMode === "github-api") {
+      return this.octokit.rest.git
+        .createRef({
+          ...context.repo,
+          ref: `refs/tags/${tag}`,
+          sha: context.sha,
+        })
+        .catch((err) => {
+          // Assuming tag was manually pushed in custom publish script
+          core.warning(`Failed to create tag ${tag}: ${err.message}`);
+        });
+    }
+    await exec("git", ["push", "origin", tag], {
+      cwd: this.cwd,
+      env: {
+        ...process.env,
+        ...this.#getCliAuthEnv(),
+      } as Record<string, string>,
+    });
+  }
+
+  async prepareBranch(branch: string) {
+    if (this.commitMode === "github-api") {
+      // Preparing a new local branch is not necessary when using the API
+      return;
+    }
+    await switchToMaybeExistingBranch(branch, { cwd: this.cwd });
+    await reset(context.sha, { cwd: this.cwd });
+  }
+
+  async pushChanges({ branch, message }: { branch: string; message: string }) {
+    if (this.commitMode === "github-api") {
+      /**
+       * Only add files form the current working directory
+       *
+       * This will emulate the behavior of `git add .`,
+       * used in {@link commitAll}.
+       */
+      const addFromDirectory = this.cwd;
+      return commitChangesFromRepo({
+        octokit: this.octokit,
+        ...context.repo,
+        branch,
+        message,
+        base: {
+          commit: context.sha,
+        },
+        cwd: this.cwd,
+        force: true,
+      });
+    }
+    if (!(await checkIfClean({ cwd: this.cwd }))) {
+      await commitAll(message, { cwd: this.cwd });
+    }
+    await push(branch, {
+      cwd: this.cwd,
+      env: {
+        ...process.env,
+        ...this.#getCliAuthEnv(),
+      } as Record<string, string>,
+    });
+  }
+}