feat(update): implement

Close #300

test/cli.ts

@@ -1,6 +1,12 @@
 import path = require('path')
-import test = require('tape')
+import tape = require('tape')
+import promisifyTape from 'tape-promise'
+const test = promisifyTape(tape)
 import spawn = require('cross-spawn')
+import exists = require('exists-file')
+import {add as addDistTag} from './support/distTags'
+import prepare from './support/prepare'
+import runCli from './support/run-cli'
 
 const pnpmBin = path.join(__dirname, '../src/bin/pnpm.ts')
 
@@ -11,3 +17,21 @@ test('return error status code when underlying command fails', t => {
 
   t.end()
 })
+
+test('update', async function (t) {
+  prepare()
+
+  const latest = 'stable'
+
+  await addDistTag('dep-of-pkg-with-1-dep', '1.0.0', latest)
+
+  await runCli('install', 'pkg-with-1-dep', '-S', '--tag', latest, '--cache-ttl', '0')
+
+  t.ok(await exists('node_modules/.store/dep-of-pkg-with-1-dep@1.0.0'), 'should install dep-of-pkg-with-1-dep@1.0.0')
+
+  await addDistTag('dep-of-pkg-with-1-dep', '1.1.0', latest)
+
+  await runCli('update', '--depth', '1', '--tag', latest)
+
+  t.ok(await exists('node_modules/.store/dep-of-pkg-with-1-dep@1.1.0'), 'should update to dep-of-pkg-with-1-dep@1.1.0')
+})

test/support/run-cli.ts

@@ -0,0 +1,17 @@
+import path = require('path')
+import crossSpawn = require('cross-spawn')
+
+const pnpmBin = path.join(__dirname, '../../src/bin/pnpm.ts')
+
+export default function (...args: string[]) {
+  return new Promise((resolve, reject) => {
+    const proc = crossSpawn.spawn('ts-node', [pnpmBin].concat(args), {stdio: 'inherit'})
+
+    proc.on('error', reject)
+
+    proc.on('close', (code: number) => {
+      if (code > 0) return reject(new Error('Exit code ' + code))
+      resolve()
+    })
+  })
+}