Add Setuptools integration issue #261

These changes enable any user that installs `isort` to check his source
code from setup.py with the command `python setup.py isort`

I also checked isort package code with his command in tox and travis.

Acknowledgements: this is mostly inspired by flake8 setuptools integration,
see [flake8 doc](http://flake8.readthedocs.org/en/2.2.3/setuptools.html)

6 files changed, 127 insertions, 16 deletions

diff --git a/.editorconfig b/.editorconfig
index e2da10c7..5e1a36e2 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -9,4 +9,12 @@ known_third_party = kate
 ignore_frosted_errors = E103
 skip = runtests.py,build
 balanced_wrapping = true
-not_skip = __init__.py
\ No newline at end of file
+not_skip = __init__.py
+
+[*.{rst,ini}]
+indent_style = space
+indent_size = 4
+
+[*.yml]
+indent_style = space
+indent_size = 2
diff --git a/.travis.yml b/.travis.yml
index 02bae897..5ed06553 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,13 @@
 language: python
-python:
-  - "pypy"
-  - "2.6"
-  - "2.7"
-  - "3.2"
-  - "3.3"
-  - "3.4"
-script: python setup.py test
+env:
+  - TOXENV=isort-check
+  - TOXENV=py26
+  - TOXENV=py27
+  - TOXENV=py32
+  - TOXENV=py33
+  - TOXENV=py34
+  - TOXENV=pypy
+install:
+  - pip install tox
+script:
+  - tox -e $TOXENV
diff --git a/README.md b/README.md
index f055af35..cf959abb 100644
--- a/README.md
+++ b/README.md
@@ -385,7 +385,10 @@ or:
     menu > Python > Remove Import
 
 Using isort to verify code
-======================
+==========================
+
+The ```--check-only``` option
+-----------------------------
 
 isort can also be used to used to verify that code is correctly formatted by running it with -c.
 Any files that contain incorrectly sorted imports will be outputted to stderr.
@@ -403,7 +406,7 @@ Which can help to ensure a certain level of code quality throughout a project.
 
 
 Git hook
-========
+--------
 
 isort provides a hook function that can be integrated into your Git pre-commit script to check
 Python code before committing.
@@ -419,6 +422,31 @@ To cause the commit to fail if there are isort errors (strict mode), include the
 If you just want to display warnings, but allow the commit to happen anyway, call git_hook without
 the `strict` parameter.
 
+Setuptools integration
+----------------------
+
+Upon installation, isort enables a setuptools command that checks Python files
+declared by your project.
+
+Running ``python setup.py isort`` on the command line will check the files
+listed in your ``py_modules`` and ``packages``.  If any warning is found,
+the command will exit with an error code::
+
+    $ python setup.py isort
+
+Also, to allow users to be able to use the command without having to install
+isort themselves, add isort to the setup_requires of your setup() like so::
+
+    setup(
+        name="project",
+        packages=["project"],
+
+        setup_requires=[
+            "isort"
+        ]
+    )
+
+
 
 Why isort?
 ======================
diff --git a/isort/main.py b/isort/main.py
index c10405c1..a51bc5cf 100755
--- a/isort/main.py
+++ b/isort/main.py
@@ -21,12 +21,15 @@ OTHER DEALINGS IN THE SOFTWARE.
 from __future__ import absolute_import, division, print_function, unicode_literals
 
 import argparse
+import glob
 import os
 import sys
 
+import setuptools
 from pies.overrides import *
 
 from isort import SECTION_NAMES, SortImports, __version__
+from isort.settings import default, from_path
 
 
 def iter_source_code(paths):
@@ -41,7 +44,62 @@ def iter_source_code(paths):
             yield path
 
 
-def main():
+class ISortCommand(setuptools.Command):
+    """The :class:`ISortCommand` class is used by setuptools to perform
+    imports checks on registered modules.
+    """
+
+    description = "Run isort on modules registered in setuptools"
+    user_options = []
+
+    def initialize_options(self):
+        default_settings = default.copy()
+        for (key, value) in itemsview(default_settings):
+            setattr(self, key, value)
+
+    def finalize_options(self):
+        "Get options from config files."
+        self.arguments = {}
+        computed_settings = from_path(os.getcwd())
+        for (key, value) in itemsview(computed_settings):
+            self.arguments[key] = value
+
+    def distribution_files(self):
+        """Find distribution packages."""
+        # This is verbatim from flake8
+        if self.distribution.packages:
+            package_dirs = self.distribution.package_dir or {}
+            for package in self.distribution.packages:
+                pkg_dir = package
+                if package in package_dirs:
+                    pkg_dir = package_dirs[package]
+                elif '' in package_dirs:
+                    pkg_dir = package_dirs[''] + os.path.sep + pkg_dir
+                yield pkg_dir.replace('.', os.path.sep)
+
+        if self.distribution.py_modules:
+            for filename in self.distribution.py_modules:
+                yield "%s.py" % filename
+        # Don't miss the setup.py file itself
+        yield "setup.py"
+
+    def run(self):
+        arguments = self.arguments
+        wrong_sorted_files = False
+        arguments['check'] = True
+        for path in self.distribution_files():
+            for python_file in glob.iglob(os.path.join(path, '*.py')):
+                try:
+                    incorrectly_sorted = SortImports(python_file, **arguments).incorrectly_sorted
+                    if incorrectly_sorted:
+                        wrong_sorted_files = True
+                except IOError as e:
+                    print("WARNING: Unable to parse file {0} due to {1}".format(file_name, e))
+        if wrong_sorted_files:
+            exit(1)
+
+
+def create_parser():
     parser = argparse.ArgumentParser(description='Sort Python import definitions alphabetically '
                                                  'within logical sections.')
     parser.add_argument('files', nargs='+', help='One or more Python source files that need their imports sorted.')
@@ -64,7 +122,7 @@ def main():
                         help='Force sortImports to recognize a module as being part of the current python project.')
     parser.add_argument('-m', '--multi_line', dest='multi_line_output', type=int, choices=[0, 1, 2, 3, 4, 5],
                         help='Multi line output (0-grid, 1-vertical, 2-hanging, 3-vert-hanging, 4-vert-grid, '
-                            '5-vert-grid-grouped).')
+                        '5-vert-grid-grouped).')
     parser.add_argument('-i', '--indent', help='String to place for indents defaults to "    " (4 spaces).',
                         dest='indent', type=str)
     parser.add_argument('-a', '--add_import', dest='add_imports', action='append',
@@ -116,6 +174,10 @@ def main():
                         help='Force from imports to be grid wrapped regardless of line length')
 
     arguments = dict((key, value) for (key, value) in itemsview(vars(parser.parse_args())) if value)
+    return arguments
+
+def main():
+    arguments = create_parser()
     file_names = arguments.pop('files', [])
 
     if file_names == ['-']:
diff --git a/setup.py b/setup.py
index 124bea32..f51220f7 100755
--- a/setup.py
+++ b/setup.py
@@ -53,7 +53,8 @@ setup(name='isort',
       entry_points={
         'console_scripts': [
             'isort = isort.main:main',
-        ]
+        ],
+        'distutils.commands': ['isort = isort.main:ISortCommand'],
       },
       packages=['isort'],
       requires=['pies', 'natsort'],
diff --git a/tox.ini b/tox.ini
index d8d7b905..94f069d7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,9 +4,17 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py26, py27, py32, py33, py34, pypy
+envlist =
+    isort-check,
+    py26, py27, py32, py33, py34, pypy
 
 [testenv]
-commands = py.test {posargs}
+commands = 
+    py.test {posargs}
 deps =
     pytest
+
+[testenv:isort-check]
+commands = 
+    python setup.py isort
+deps =