duplicates:

• SR-1195 Dependency names that differ only in case cause conflicts

Issue Description:

Here is a simple Package.swift that shows the issue:

import PackageDescription

let package = Package(
    name: "spm-strict-url-comparison",
    dependencies: [
       .Package(url: "https://github.com/IBM-Swift/SwiftyJSON.git", majorVersion: 15),
       .Package(url: "https://github.com/IBM-Swift/SwiftyJSON", majorVersion: 15)
    ]
)

The only difference between the two URLs is the `.git`. On Swift 3.0.2, this causes an error in the package fetch stage. On Swift 3.1 2/15 snapshot, package fetch succeeds, but compiling stage returns errors (because the same classes are fetched twice).

If I add `.git` to the second URL, Swift 3.0.2 is able to recognize the duplicate repo and fetch correctly.

The bigger issue is that if both dependency A and B fetch dependency C, but the URLs in A and B that point to C differ in the `.git`, this causes errors even though the URLs are still technically correct.

Issue originally identified in the public Swift@IBM Slack: https://swift-at-ibm.slack.com/archives/kitura/p1487266218001148