chore(tests): test-initialization via script

Fixes #478

Author: Byron

Diff for: .travis.yml

@@ -19,12 +19,7 @@ install:
   - pip install coveralls flake8 sphinx
 
   # generate some reflog as git-python tests need it (in master)
-  - git tag __testing_point__
-  - git checkout master || git checkout -b master
-  - git reset --hard HEAD~1
-  - git reset --hard HEAD~1
-  - git reset --hard HEAD~1
-  - git reset --hard __testing_point__
+  - ./init-tests-after-clone.sh
 
   # as commits are performed with the default user, it needs to be set for travis too
   - git config --global user.email "travis@ci.com"

Diff for: README.md

@@ -34,16 +34,29 @@ Both commands will install the required package dependencies.
 A distribution package can be obtained for manual installation at:
 
     http://pypi.python.org/pypi/GitPython
+    
+If you like to clone from source, you can do it like so:
+
+```bash
+git clone https://github.com/gitpython-developers/GitPython
+git submodule update --init --recursive
+./init-tests-after-clone.sh
+```
 
 ### RUNNING TESTS
 
+*Important*: Right after cloning this repository, please be sure to have executed the `init-tests-after-clone.sh` script in the repository root. Otherwise you will encounter test failures.
+
 The easiest way to run test is by using [tox](https://pypi.python.org/pypi/tox) a wrapper around virtualenv. It will take care of setting up environnements with the proper dependencies installed and execute test commands. To install it simply:
 
     pip install tox
 
 Then run:
 
     tox
+    
+    
+For more fine-grained control, you can use `nose`.
 
 ### Contributions
 

Diff for: init-tests-after-clone.sh

@@ -0,0 +1,15 @@
+#!/bin/bash -e
+
+if [[ -z "$TRAVIS" ]]; then
+  read -p "This operation will destroy locally modified files. Continue ? [N/y]: " answer
+  if [[ ! $answer =~ [yY] ]]; then
+    exit 2
+  fi
+fi
+
+git tag __testing_point__
+git checkout master || git checkout -b master
+git reset --hard HEAD~1
+git reset --hard HEAD~1
+git reset --hard HEAD~1
+git reset --hard __testing_point__