Don't override user specified depth in outdated

Restores ability to update packages using `--depth` as suggested by `npm audit`.

i.e `npm update eslint-utils --depth 2`.

PR-URL: #239
Credit: @G-Rath
Close: #239
Reviewed-by: @claudiahdz

lib/outdated.js

@@ -91,7 +91,7 @@ function outdated (args, silent, cb) {
   var dir = path.resolve(npm.dir, '..')
 
   // default depth for `outdated` is 0 (cf. `ls`)
-  if (opts.depth) opts = opts.concat({depth: 0})
+  if (opts.depth === Infinity) opts = opts.concat({depth: 0})
 
   readPackageTree(dir, andComputeMetadata(function (er, tree) {
     if (!tree) return cb(er)

test/tap/outdated-depth.js

@@ -47,19 +47,30 @@ test('outdated depth zero', function (t) {
   mr({ port: common.port }, function (er, s) {
     npm.load(
       {
+        depth: 0,
         loglevel: 'silent',
         registry: common.registry
       },
       function () {
         npm.install('.', function (er) {
           if (er) throw new Error(er)
           npm.outdated(function (err, d) {
-            t.ifError(err, 'npm outdated ran without error')
+            if (err) {
+              throw err
+            }
             t.is(process.exitCode, 1, 'exit code set to 1')
             process.exitCode = 0
             t.deepEqual(d[0], expected)
-            s.close()
-            t.end()
+            t.equal(d.length, 1)
+            npm.config.set('depth', 1)
+            npm.outdated(function (err, d) {
+              t.equal(d.length, 2)
+              if (err) {
+                throw err
+              }
+              s.close()
+              t.end()
+            })
           })
         })
       }