fix: always set originalLockfileVersion when doing shrinkwrap reset

Fix: npm/cli#3899

A shrinkwrap reset without specifying a lockfile version was triggering
an old lockfile warning due to the originalLockfileVersion not being set
prior to checking whether the lockfile was old.

lib/shrinkwrap.js

@@ -380,9 +380,10 @@ class Shrinkwrap {
   reset () {
     this.tree = null
     this[_awaitingUpdate] = new Map()
-    this.originalLockfileVersion = this.lockfileVersion
+    const lockfileVersion = this.lockfileVersion || defaultLockfileVersion
+    this.originalLockfileVersion = lockfileVersion
     this.data = {
-      lockfileVersion: this.lockfileVersion || defaultLockfileVersion,
+      lockfileVersion,
       requires: true,
       packages: {},
       dependencies: {},

test/arborist/build-ideal-tree.js

@@ -611,6 +611,16 @@ t.test('force a new mkdirp (but not semver major)', async t => {
   t.equal(arb.idealTree.children.get('minimist').package.version, '1.2.5')
 })
 
+t.test('empty update should not trigger old lockfile', async t => {
+  const path = resolve(fixtures, 'empty-update')
+  const checkLogs = warningTracker()
+
+  const arb = newArb(path)
+  await arb.reify({ update: true })
+
+  t.strictSame(checkLogs(), [])
+})
+
 t.test('no fix available', async t => {
   const path = resolve(fixtures, 'audit-mkdirp/mkdirp-unfixable')
   const checkLogs = warningTracker()

test/fixtures/empty-update/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "empty-update",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "devDependencies": {},
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}