Fix ls depth when outputting json

[MarkReeder]

This fixes the depth option when used in combination with the json option.

As an example, prior to this diff:

npm ls -depth=0

r-dom@2.1.0 /root/temp/r-dom
├── classnames@1.2.2
├── for-each@0.3.2
...

npm ls -depth=0 --json

{
  "name": "r-dom",
  "version": "2.1.0",
  "dependencies": {
    "classnames": {
      "version": "1.2.2",
      "from": "classnames@^1.1.4",
      "resolved": "https://registry.npmjs.org/classnames/-/classnames-1.2.2.tgz"
    },
    "for-each": {
      "version": "0.3.2",
      "from": "for-each@^0.3.2",
      "resolved": "https://registry.npmjs.org/for-each/-/for-each-0.3.2.tgz",
      "dependencies": {
        "is-function": {
          "version": "1.0.1",
          "from": "is-function@~1.0.0",
          "resolved": "https://registry.npmjs.org/is-function/-/is-function-1.0.1.tgz"
        }
      }
    },
...

and after this change:

npm ls -depth=0

r-dom@2.1.0 /root/temp/r-dom
├── classnames@1.2.2
├── for-each@0.3.2
...

npm ls -depth=0 --json

{
  "name": "r-dom",
  "version": "2.1.0",
  "dependencies": {
    "classnames": {
      "version": "1.2.2",
      "from": "classnames@^1.1.4",
      "resolved": "https://registry.npmjs.org/classnames/-/classnames-1.2.2.tgz"
    },
    "for-each": {
      "version": "0.3.2",
      "from": "for-each@^0.3.2",
      "resolved": "https://registry.npmjs.org/for-each/-/for-each-0.3.2.tgz"
    },
...

Note that the dependencies of for-each are incorrectly included prior and correctly excluded after.

[othiym23]

This looks good! It needs a test before it can be landed, though. We're in the process of doing a bunch of work to the npm tests, and part of that will be writing a new guide on how to write a good npm test, but in the meantime, if you want to take a look at what's in test/tap and copypasta one of the existing tests, that would be a good start. Thanks for putting this together!

[MarkReeder]

I added some tests a couple days ago. They're copypasta'd from similar tests in test/tap/ls-depth-cli.js - let me know if you'd like me to make any changes.

[lxe]

Ah I am observing this issue as well. Would be nice to get this merged!

[othiym23]

Merged and rebased and landed for npm@3 as 71c9590. Will do the same for npm@2 shortly.

[othiym23]

Cherry-picked for npm@2 as f482664. Thanks for putting this together, and thanks for adding the tests!