Test for go-git issue #647

This is a test for go-git issue #647.

The server in main.go serves the repository of the current working directory on http://localhost:8080.

To reproduce the error, you can either run the test with go test ./... or manually as follows:

1. Start the git HTTP server:

   go run main.go

2. In a separate terminal, run the following:

   git clone --no-progress http://localhost:8080

3. You should see an output similar to this:

   Cloning into 'localhost'...
   fatal: protocol error: bad line length character: PACK
   fatal: protocol error: bad pack header