add 'cython' command to setup.py

setup.py

@@ -40,15 +40,7 @@ sources = ['gevent/core.c']
 libraries = []
 
 
-class my_build_ext(build_ext.build_ext):
-    user_options = (build_ext.build_ext.user_options
-                    + [("cython=", None, "path to the cython executable")])
-
-    def initialize_options(self):
-        build_ext.build_ext.initialize_options(self)
-        self.cython = "cython"
-
-    def compile_cython(self):
+def run_cython(cython_command='cython'):
     sources = glob.glob('gevent/*.pyx') + glob.glob('gevent/*.pxi')
     if not sources:
         if not os.path.exists('gevent/core.c'):
@@ -58,21 +50,30 @@ class my_build_ext(build_ext.build_ext):
         changed = [filename for filename in sources if (os.stat(filename).st_mtime - core_c_mtime) > 1]
         if not changed:
             return
-            print >> sys.stderr, 'Running %s (changed: %s)' % (self.cython, ', '.join(changed))
+        print >> sys.stderr, 'Running %s (changed: %s)' % (cython_command, ', '.join(changed))
     else:
-            print >> sys.stderr, 'Running %s' % self.cython
-        cython_result = os.system('%s gevent/core.pyx' % self.cython)
+        print >> sys.stderr, 'Running %s' % cython_command
+    cython_result = os.system('%s gevent/core.pyx' % cython_command)
     if cython_result:
-            if os.system('%s -V 2> %s' % (self.cython, os.devnull)):
+        if os.system('%s -V 2> %s' % (cython_command, os.devnull)):
             # there's no cython in the system
             print >> sys.stderr, 'No cython found, cannot rebuild core.c'
             return
         sys.exit(1)
 
+
+class my_build_ext(build_ext.build_ext):
+    user_options = (build_ext.build_ext.user_options
+                    + [("cython=", None, "path to the cython executable")])
+
+    def initialize_options(self):
+        build_ext.build_ext.initialize_options(self)
+        self.cython = "cython"
+
     def build_extension(self, ext):
         compile_libevent(self)
         if self.cython:
-            self.compile_cython()
+            run_cython(self.cython)
         result = build_ext.build_ext.build_extension(self, ext)
         # hack: create a symlink from build/../core.so to gevent/core.so
         # to prevent "ImportError: cannot import name core" failures
@@ -295,6 +296,9 @@ def read(name):
 
 
 if __name__ == '__main__':
+    if sys.argv[1:] == ['cython']:
+        run_cython()
+    else:
         setup(
             name='gevent',
             version=__version__,