A little script to:
===================
* fetch upstream repositories
* automatically build them
* automatically install them into a virtualenv
* The virtualenv folder can be coosen with the $VENV environment variable.


Format of .repo file:
=====================
The .repo file consists of three columns (ONLY! More columns are not allowed!).
* $1: SCM type (currently only hg/git supported)
* $2: name, where the repository will be checked out
* $3: url of the repository on the web


Custom BUILD/INSTALL scripts:
=============================
Some repositories don't conform to the usual `python setup.py build` convention
and need a custom BUILD and or INSTALL script.
This is now supported with placing a executable $scm.BUILD or $scm.INSTALL
script into the checked out repository (take yt as an example).


Example workflow
================

* bootstrap virtualenv:
  `./manage.sh clone virtualenv.repo`

* create `ipython` virtualenv in ~/venv/ipython
  `./manage.sh create_env ipython`

* activate it:
  `. ~/venv/ipython/bin/activate`

* clone dependencies of ipython:
  `./manage.sh clone ipython.repo`

* build dependencies of ipython:
  `./manage.sh build ipython.repo`
  This currently fails, as you first need to build/install cython with:
  `cd ipython/cython && python setup.py build` and rerun:
  `./manage.sh build ipython.repo`

  This overhead is solved with running `./manage.sh binstall ipython.repo`
  instead, which does builing and installing in one step.

* install dependencies of ipython:
  `./manage.sh install ipython.repo`

* test correct location of `ipython` command:
  `which ipython` -> ~/venv/ipython/bin/ipython

* run testsuite of ipython:
  `iptest`