Don't forget version at the end of setup.py, write it only if changed.

This fixes issue159: "python setup.py install" shouldn't write new files
in the working dir if one has done "python setup.py build" first.

mercurial/version.py

@@ -28,8 +28,15 b' def get_version():'
 
 def write_version(version):
     """Overwrite version file."""
-    filename = os.path.join(os.path.dirname(__file__), '__version__.py')
-    f = open(filename, 'w')
+    if version == get_version():
+        return
+    directory = os.path.dirname(__file__)
+    for suffix in ['py', 'pyc', 'pyo']:
+        try:
+            os.unlink(os.path.join(directory, '__version__.%s' % suffix))
+        except OSError:
+            pass
+    f = open(os.path.join(directory, '__version__.py'), 'w')
     f.write("# This file is auto-generated.\n")
     f.write("version = %r\n" % version)
     f.close()

setup.py

@@ -72,7 +72,6 b' class install_package_data(install_data)'
                                    ('install_lib', 'install_dir'))
         install_data.finalize_options(self)
 
-try:
     mercurial.version.remember_version(version)
     cmdclass = {'install_data': install_package_data}
     py2exe_opts = {}
@@ -102,5 +101,3 b' try:'
                                        readme='contrib/macosx/Readme.html',
                                        welcome='contrib/macosx/Welcome.html')),
           **py2exe_opts)
-finally:
-    mercurial.version.forget_version()