git-node: add git-node-release (#388)

This PR constitutes the first portion of an automated release flow to abstract away the tedious aspects of preparing and promoting releases.

The preparation and promotion aspects of this new flow will be split into two separate PRs for easier review, so this is just the preparation step, with the promotion step marked as a TODO for implementation in a subsequent PR.

Author: codebytere

components/git/release.js

@@ -0,0 +1,91 @@
+'use strict';
+
+const yargs = require('yargs');
+
+const CLI = require('../../lib/cli');
+const ReleasePreparation = require('../../lib/prepare_release');
+const { runPromise } = require('../../lib/run');
+
+const PREPARE = 'prepare';
+const PROMOTE = 'promote';
+
+const releaseOptions = {
+  prepare: {
+    describe: 'Prepare a new release of Node.js',
+    type: 'boolean'
+  },
+  promote: {
+    describe: 'Promote new release of Node.js',
+    type: 'boolean'
+  },
+  security: {
+    describe: 'Demarcate the new security release as a security release',
+    type: 'boolean'
+  }
+};
+
+function builder(yargs) {
+  return yargs
+    .options(releaseOptions).positional('newVersion', {
+      describe: 'Version number of the release to be prepared or promoted'
+    })
+    .example('git node release --prepare 1.2.3',
+      'Prepare a new release of Node.js tagged v1.2.3');
+}
+
+function handler(argv) {
+  if (argv.prepare) {
+    return release(PREPARE, argv);
+  } else if (argv.promote) {
+    return release(PROMOTE, argv);
+  }
+
+  // If more than one action is provided or no valid action
+  // is provided, show help.
+  yargs.showHelp();
+}
+
+function release(state, argv) {
+  const logStream = process.stdout.isTTY ? process.stdout : process.stderr;
+  const cli = new CLI(logStream);
+  const dir = process.cwd();
+
+  return runPromise(main(state, argv, cli, dir)).catch((err) => {
+    if (cli.spinner.enabled) {
+      cli.spinner.fail();
+    }
+    throw err;
+  });
+}
+
+module.exports = {
+  command: 'release [newVersion|options]',
+  describe:
+    'Manage an in-progress release or start a new one.',
+  builder,
+  handler
+};
+
+async function main(state, argv, cli, dir) {
+  if (state === PREPARE) {
+    const prep = new ReleasePreparation(argv, cli, dir);
+
+    if (prep.warnForWrongBranch()) return;
+
+    // If the new version was automatically calculated, confirm it.
+    if (!argv.newVersion) {
+      const create = await cli.prompt(
+        `Create release with new version ${prep.newVersion}?`,
+        { defaultAnswer: true });
+
+      if (!create) {
+        cli.error('Aborting release preparation process');
+        return;
+      }
+    }
+
+    return prep.prepare();
+  } else if (state === PROMOTE) {
+    // TODO(codebytere): implement release promotion.
+  }
+}