Why does leiningen make a directory hierarchy? Can I dispense with it?

Question

If I create a new clojure project with leiningen, it makes a directory tree like so:

.
|-- doc
|   `-- intro.md
|-- project.clj
|-- README.md
|-- src
|   `-- hello_friend
|       `-- core.clj
`-- test
    `-- hello_friend
        `-- core_test.clj

Often, all I want is a single clojure file, and I want to use leiningen to handle libraries and start a repl.

I've got two questions:

(1) Is is possible to get leiningen to work properly with this structure

.
|-- project.clj
`-- hello.clj

which I'd greatly prefer. (In fact even better would be to have the project.clj as part of the hello.clj file)

(2) Is there any good reason for the deep directory structure? Or is it just a habit from java-land?

---

Note, this works fine as far as I can see:

project.clj

(defproject generic "0.0.0"
  :dependencies 
  [[org.clojure/clojure "1.4.0"]
   [hiccup "1.0.2"]]
  :source-paths ["."]
  :main two

  :repl-options { :port 4001 :init (println "(-main) to run") }
)

one.clj

(ns one
  (:use hiccup.core))

(def doom (html [:h1 "doom"]))

two.clj

(ns two 
  (:require one))

(defn -main [] 
  (println one/doom))

Answer 1

(1) You can specify :source-paths ["."] in your project.clj. See lein sample project for all possible options

(2) You need the "deep" structure once you have 2 namespaces and one requires on the other. See here for an explanation of how namespaces are mapped to files.