show update warning

bin/build

@@ -37,6 +37,7 @@ cd $WORKSPACE
 yarn install --offline --no-progress --production
 
 echo $VERSION > VERSION
+echo $BRANCH > BRANCH
 
 # create bin runner
 cat << EOF > heroku

lib/branch.js

@@ -0,0 +1,10 @@
+const fs = require('fs-extra')
+const path = require('path')
+let branch
+try {
+  branch = fs.readFileSync(path.join(__dirname, '..', 'BRANCH'), 'utf-8').trim()
+} catch (err) {
+  branch = 'v6'
+}
+
+module.exports = branch

lib/commands/update.js

@@ -4,32 +4,38 @@ const {Command} = require('heroku-cli-command')
 const path = require('path')
 const dirs = require('../dirs')
 const version = require('../version')
+const currentBranch = require('../branch')
 const lock = require('rwlockfile')
+const config = require('../config')
 
 class Update extends Command {
   async run () {
     this.fs = require('fs-extra')
-    this.got = require('got')
-    this.branch = 'v6'
     this.action('heroku-cli: Updating CLI')
-    this.manifest = await this.fetchManifest()
-    if (this.flags.force || version !== this.manifest.version) {
+    this.manifest = await this.constructor.fetchManifest(this.args.branch || currentBranch)
+    if (!this.flags.force && version === this.manifest.version) {
+      this.action.done(`already on latest version: ${version}`)
+    } else if (!this.flags.force && config.updateDisabled) {
+      this.action.done(`not updating CLI: ${config.updateDisabled}`)
+    } else {
       this.action(`heroku-cli: Updating CLI to ${this.color.green(this.manifest.version)}${this.branch === 'stable' ? '' : ' (' + this.color.yellow(this.branch) + ')'}`)
       await this.update()
       this.action.done()
-    } else this.action.done(`already on latest version: ${version}`)
+    }
     this.action('heroku-cli: Updating plugins')
   }
 
-  async fetchManifest () {
-    let url = `https://cli-assets.heroku.com/branches/${this.branch}/${process.platform}-${process.arch}`
-    let {body: manifest} = await this.got(url, {json: true})
+  static async fetchManifest (branch) {
+    const got = require('got')
+    let url = `https://cli-assets.heroku.com/branches/${branch}/${process.platform}-${process.arch}`
+    let {body: manifest} = await got(url, {json: true})
     return manifest
   }
 
   async update () {
+    const got = require('got')
     let url = `https://cli-assets.heroku.com/branches/${this.branch}/${this.base}.tar.gz`
-    let stream = await this.got.stream(url)
+    let stream = await got.stream(url)
     let dir = path.join(dirs.data, 'jscli')
     let tmp = path.join(dirs.data, 'jscli_tmp')
     await this.extract(stream, tmp)
@@ -98,12 +104,21 @@ class Update extends Command {
   }
 
   static async autoupdate () {
+    if (!this.autoupdateNeeded) return
+    if (config.updateDisabled) return await this.warnIfUpdateAvailable()
     const fs = require('fs-extra')
     fs.writeFileSync(dirs.autoupdatefile, '')
     const {spawn} = require('child_process')
     spawn('heroku', ['update'])
   }
 
+  static async warnIfUpdateAvailable () {
+    const manifest = await this.fetchManifest(currentBranch)
+    if (version !== manifest.version) {
+      console.error(`heroku-cli: update available from ${version} to ${manifest.version}`)
+    }
+  }
+
   /**
    * checks if there is an update running
    * if there is an update running, it waits for it to complete, then restarts the CLI
@@ -116,12 +131,15 @@ class Update extends Command {
       await this.restartCLI()
     } else {
       await lock.read(dirs.updatelockfile)
-      if (this.autoupdateNeeded) await this.autoupdate()
+      await this.autoupdate()
     }
   }
 }
 
 Update.topic = 'update'
+Update.args = [
+  {name: 'branch', optional: true}
+]
 Update.flags = [
   {name: 'force', char: 'f', hidden: true}
 ]

lib/config.js

@@ -0,0 +1 @@
+exports.updateDisabled = 'running from npm'

lib/version.js

@@ -1,4 +1,4 @@
-const fs = require('fs')
+const fs = require('fs-extra')
 const path = require('path')
 let version
 try {