[BUG] npm 7 confusing error when installing git dependency with invalid commit-ish

[Coridyn]

Current Behavior:

Attempting to install a git dependency with an invalid commit-ish gives a very confusing error that doesn't explain the cause of the problem.

npm@7 should give an error that indicates it can't find a commit with that hash.

npm@6 does give a useful error for this same scenario.

Steps To Reproduce:

package.json

{
  "dependencies": {
    "bad-commitish": "git@github.com:npm/json-parse-even-better-errors.git#bad-commitish"
  }
}

npm 7

$ npm --version
7.0.0-beta.10

$ npm install
npm ERR! code 128
npm ERR! command failed
npm ERR! command git clone --mirror -q ssh://git@github.com/npm/json-parse-even-better-errors.git /home/coridyn/.npm/_cacache/tmp/git-clone-65ca3462/.git
npm ERR! fatal: destination path '/home/coridyn/.npm/_cacache/tmp/git-clone-65ca3462/.git' already exists and is not an empty directory.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/coridyn/.npm/_logs/2020-09-09T08_07_35_128Z-debug.log

---

npm 6

npm 6 shows a better message for the same scenario

$ npm --version
6.14.8

$ npm install
npm ERR! code 1
npm ERR! Command failed: git checkout bad-commitish
npm ERR! error: pathspec 'bad-commitish' did not match any file(s) known to git.
npm ERR!

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/coridyn/.npm/_logs/2020-09-09T08_06_45_815Z-debug.log

Environment:

This occurs in both Windows and Linux npm 7.0.0-beta.10.

$ node --version
v12.16.2

$ npm --version
7.0.0-beta.10

[wraithgar]

A duplicate issue was created and it is the one we are using for tracking this #3149