How to use `$ swift build --fetch`

SwiftBuildFetchQuestions.md

#Overview

I had seen the following:

https://github.com/apple/swift-package-manager/blob/swift-DEVELOPMENT-SNAPSHOT-2016-03-24-a/Sources/Get/Fetcher.swift#L78-L86

so I tried to run the $ swift build --fetch command.

• The first $ swift build --fetch has succeeded.
• The second $ swift build --fetch has failed without running $ swift build --clean=dist.

Questions

• Am I using it the wrong way?
• By any chance, hasn't $ swift build --fetch supported in these situation yet?

Environments

• OS X 10.11.4
• swift-DEVELOPMENT-SNAPSHOT-2016-03-24-a

The Manifest File

import PackageDescription

let package = Package(
    name: "MyProject",
    dependencies: [
        .Package(url: "../Pokemon", versions: Version(1,0,0)..<Version(2,0,0)),
    ]
)

The lasted tag of Pokemon is 1.7.0.

Operations

1. Run $ swift build --clean=dist.
2. Run $ swift build --fetch , then Pokemon is updated to 1.7.0.
3. Run $ git tag 1.8.0 against Pokemon , then the lasted tag of Pokemon is 1.8.0.
4. Run $ swift build --fetch , then Pokemon is not updated.
5. Run $ swift build --clean=dist.
6. Run $ swift build --fetch , then Pokemon is updated to 1.8.0.

I expected Pokemon had updated to 1.8.0 with the 4th operation.