feat: suggest gh pr commands to finish landing (#583)

Also make the output easier to copy and paste.

lib/landing_session.js

@@ -11,7 +11,7 @@ const {
   runAsync, runSync, forceRunAsync
 } = require('./run');
 const Session = require('./session');
-const { shortSha } = require('./utils');
+const { shortSha, isGhAvailable } = require('./utils');
 
 const isWindows = process.platform === 'win32';
 
@@ -416,11 +416,16 @@ class LandingSession extends Session {
     }
 
     this.cleanFiles();
-    cli.log('Temporary files removed');
+    cli.log('Temporary files removed.');
     cli.log('To finish landing:');
-    cli.log(`1. Run \`git push ${upstream} ${branch}\``);
+    cli.log('1. Run: ');
+    cli.log(`   git push ${upstream} ${branch}`);
     const url = `https://github.com/${owner}/${repo}/pull/${prid}`;
     cli.log(`2. Post "Landed in ${willBeLanded}" in ${url}`);
+    if (isGhAvailable()) {
+      cli.log(`   gh pr comment ${prid} --body "Landed in ${willBeLanded}"`);
+      cli.log(`   gh pr close ${prid}`);
+    }
   }
 
   async continue() {

lib/utils.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const which = require('which');
+
 exports.ascending = function(a, b) {
   if (a === b) return 0;
   return a < b ? -1 : 1;
@@ -26,3 +28,11 @@ exports.flatten = flatten;
 exports.shortSha = function shortSha(sha) {
   return sha.slice(0, 12);
 };
+
+let isGhAvailableCache;
+exports.isGhAvailable = function isGhAvailable() {
+  if (isGhAvailableCache === undefined) {
+    isGhAvailableCache = which.sync('gh', { nothrow: true }) !== null;
+  }
+  return isGhAvailableCache;
+};

package.json

@@ -51,6 +51,7 @@
     "proxy-agent": "^5.0.0",
     "replace-in-file": "^6.2.0",
     "rimraf": "^3.0.2",
+    "which": "^2.0.2",
     "yargs": "^16.2.0"
   },
   "devDependencies": {