diff -r fd6446a88fe3 -r aa68d35988bb Lib/packaging/command/__init__.py
--- a/Lib/packaging/command/__init__.py	Wed Jun 15 23:58:57 2011 +0200
+++ b/Lib/packaging/command/__init__.py	Thu Jun 16 17:15:53 2011 +0800
@@ -22,6 +22,7 @@
     'install_data': 'packaging.command.install_data.install_data',
     'install_distinfo':
         'packaging.command.install_distinfo.install_distinfo',
+    'develop_source': 'packaging.command.develop_source.develop_source',
     'sdist': 'packaging.command.sdist.sdist',
     'bdist': 'packaging.command.bdist.bdist',
     'bdist_dumb': 'packaging.command.bdist_dumb.bdist_dumb',
diff -r fd6446a88fe3 -r aa68d35988bb Lib/packaging/command/cmd.py
--- a/Lib/packaging/command/cmd.py	Wed Jun 15 23:58:57 2011 +0200
+++ b/Lib/packaging/command/cmd.py	Thu Jun 16 17:15:53 2011 +0800
@@ -307,6 +307,12 @@
                 setattr(self, dst_option,
                         getattr(src_cmd_obj, src_option))
 
+    def reinitialize_command(self, command, reinit_subcommands=False, **kw):
+        cmd = self.get_reinitialized_command(command, reinit_subcommands)
+        for k,v in kw.items():
+            setattr(cmd,k,v) # update command with keywords
+        return cmd
+
     def get_finalized_command(self, command, create=True):
         """Wrapper around Distribution's 'get_command_obj()' method: find
         (create if necessary and 'create' is true) the command object for
diff -r fd6446a88fe3 -r aa68d35988bb Lib/packaging/command/develop_source.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Lib/packaging/command/develop_source.py	Thu Jun 16 17:15:53 2011 +0800
@@ -0,0 +1,171 @@
+"""Develop command, which can deploy a project source in 'Development Mode'. """
+import os
+import sys
+
+from packaging import logger
+from packaging.util import (write_file, convert_path)
+from packaging.command.cmd import Command
+
+from packaging.errors import PackagingOptionError
+
+from packaging.dist import Distribution
+
+import sysconfig
+
+from sysconfig import get_paths
+
+
+class develop_source(Command):
+
+	description = "install package in 'development mode'"
+
+	# Note 4: these user options may be not complete, and should be modified or 
+	# improved in future
+	user_options = [
+		('uninstall', None, "Uninstall this source package"),
+		('multi-version', None, "Make apps have to require() a version"),
+		('install-dir', None, "Install package to DIR"),
+		('script-dir', None, "Install scripts to DIR"),
+		('exclude-scripts', None, "Don't install scripts"),
+		('always-copy', None, "Copy all needed packages to install dir"),
+		('egg-path', None, "Set the path to be used in the .dist-link file")]
+		
+	boolean_options = ['multi-version', 'always-copy', 'uninstall']
+
+	def run(self):
+		if self.uninstall:
+			self.multi_version = True
+			self.uninstall_link()
+		else:
+			self.install_for_development()
+		# self.warn_deprecated_options???
+		##
+	def initialize_options(self):
+		self.uninstall = None
+		self.dist_path = None # .dist-info directory path
+		self.install_dir = None #self.install_lib #
+		
+		self.path_file = None # the .pth file name
+		self.multi_version = None # Note 7: should be set from setup.cfg
+
+		self.always_copy_from = '.' # always copy .dist-info directory installed in curdir???
+
+	def finalize_options(self):#not complete function , need careful consideration
+		self.reinitialize_command('install_distinfo', distinfo_dir = os.curdir)
+		di = self.get_finalized_command("install_distinfo")
+		self.path_file = di.dist_name
+		# Note 2: install_distinfo always create new dist-info files, instead of copying
+		# so broken_dist_info is unuseful now
+		# if di.broken_dist_info:#Fix: does not have broken_dist_info yet !!
+		#	pass
+		#
+		# should act as easy_install.finalize_options(self) ???
+
+		# the following is to check if it is safe to install this distribution in a directory
+		# here for 'develop' command, just two files will be created in it:
+		# .pth file and .dist-link file
+
+		#-----------------may be taken as a function-------------------
+		scheme = get_paths(os.name, expand = False)
+		purelib = scheme.get('purelib')
+		if os.name == 'posix' or os.name == 'nt':
+			purelib = os.path.expanduser(purelib)
+		config_vars={}
+		config_vars['base'] = os.path.normpath(sys.prefix)
+		purelib = sysconfig._subst_vars(purelib, config_vars)#'prefix' and 'base' ???
+		self.install_dir = convert_path(purelib) # the default value of install_dir always is the purelib path, configuration of setup.cfg will be added later; should be noramlized
+		#print('installdir:'+self.install_dir)
+		#---------------------------------------------------------
+		
+		#PYTHONPATH = os.environ.get('PYTHONPATH','').split(os.pathsep)
+		#PYTHONPATH = map(normalize_path, list(filter(None, PYTHONPATH))) #python3.x format
+		sys_path = map(normalize_path, sys.path)
+		instdir = normalize_path(self.install_dir)
+		#print(instdir)
+		if instdir not in sys_path:
+			raise PackagingOptionError("'install_dir' should be contained in 'sys.path' list")
+
+		self.dist_link = os.path.join(self.install_dir, di.dist_name + '.dist-link')
+		#print('now dist info dir:'+di.distinfo_dir)
+		self.dist_base = os.path.dirname(di.distinfo_dir)# should create .dist-info directory on curdir
+		#self.dist_base = os.curdir# should always create dist-dir in place
+		if self.dist_path is None:
+			self.dist_path = os.path.abspath(self.dist_base)
+
+		target = normalize_path(self.dist_base)
+		# check --dist-path option here 
+		# Note 3: we should add a --dist-path option here
+		# it's named 'egg-path' in setuptools
+		if normalize_path(os.path.join(self.install_dir, self.dist_path)) != target:
+			raise PackagingOptionError("'dist-path' must be a relative path from the install"
+				" directory to " + target)
+
+		# Make a distribution for the package's source
+		# Is it the right way?
+		self.dist = Distribution()
+		self.dist.parse_config_files() #Note 6: add install_dir option support in setup.cfg
+		
+
+		#print('distbase:'+self.dist_base)
+		p = self.dist_base.replace(os.sep, '/') 
+		if p != os.curdir:
+			p = '../' * (p.count('/')+1)
+		self.setup_path = p
+		p = normalize_path(os.path.join(self.install_dir, self.dist_path, p))
+		if p != normalize_path(os.curdir):
+			raise PackagingOptionError("Can't get a consistent path to setup.cfg from"
+				" installation directory", p, normalize_path(os.curdir))
+
+	def install_for_development(self):# Now focus here: 2011-6-8 21:22
+		# Ensure metadata is up-to-date
+		self.run_command('install_distinfo')
+		# Build extensions in-place
+		self.reinitialize_command('build_ext', inplace=1)
+		self.run_command('build_ext')
+		#self.install_site_py() # ensure that target dir is site-safe
+		
+		# Note 1: site.py is just used by setuptools, so in packaging a proper 'site dir'
+		# does not have the need of having a site.py in it
+		
+		# Fix 1:Any 'bootstrap_install_from' here?
+		# ????
+
+		# create a .dist-link file in the installation dir, pointing to our .dist-info directory
+		logger.info("Creating %s (link to %S)", self.dist_link, self.dist_base)
+
+		if not self.dry_run:
+			f = open(self.dist_link, "w")
+			f.write(self.dist_path + "\n" + self.setup_path)
+			f.close()
+		# Fix 3: process_distribution() here??
+		# ????
+
+		# create or update the .pth file
+		self.update_path_file()
+
+	def update_path_file(self):
+		"""Creates/Updates the .pth file"""
+
+		filename = os.path.join(self.install_dir,
+                                self.path_file + ".pth")
+		
+		self.dist_location = normalize_path(self.dist_base) # shoud add other locations? be improved in future
+		
+        # Remove old .pth file and create new one if necessary
+		if os.path.islink(filename):
+			os.path.unlink(filename)
+			logger.info('removing old path file %r', filename)#warning or info?
+        
+		if not self.multi_version:
+			self.execute(write_file,
+                         (filename, [self.dist_location]), # locations?
+                         "creating %s" % filename)
+		else:
+			logger.info("'multi-version' is set, no .pth file will be created")
+
+
+
+# The following functions are taken from setuptools' pkg_resources module.
+def normalize_path(filename):
+	"""Normalize a file/dir name for comparison purposes"""
+	return os.path.normcase(os.path.realpath(filename))
\ No newline at end of file
diff -r fd6446a88fe3 -r aa68d35988bb Lib/packaging/command/install_distinfo.py
--- a/Lib/packaging/command/install_distinfo.py	Wed Jun 15 23:58:57 2011 +0200
+++ b/Lib/packaging/command/install_distinfo.py	Thu Jun 16 17:15:53 2011 +0800
@@ -61,6 +61,8 @@
             self.no_resources = False
 
         metadata = self.distribution.metadata
+        
+        self.dist_name = to_filename(safe_name(metadata['Name']))
 
         basename = "%s-%s.dist-info" % (
             to_filename(safe_name(metadata['Name'])),
diff -r fd6446a88fe3 -r aa68d35988bb Lib/packaging/develop.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Lib/packaging/develop.py	Thu Jun 16 17:15:53 2011 +0800
@@ -0,0 +1,57 @@
+"""Building blocks for different tools when excuating 'develop' command.
+
+"""
+import os
+
+from packaging import logger
+from packaging.util import (egginfo_to_distinfo, get_develop_method)
+
+from packaging.dist import Distribution
+from packaging.errors import (PackagingError, CCompilerError)
+
+
+# The function term is studying from 'install_local_project' of install.py
+def develop_local_project(path):
+	""" Deploy a project source in the 'development mode' from a source directory.
+
+	If the source directory contains a setup.py, using distutils1.
+	If a setup.cfg is found, then using the XXX command.
+	"""
+	path = os.path.abspath(path)
+	if os.path.isdir(path):
+		logger.info('deploying from source directory:%s', path)
+		_run_develop_from_dir(path)
+	else:
+		logger.warn('no projects to install')
+
+def _run_develop_from_dir(source_dir):
+	old_dir = os.getcwd()
+	os.chdir(source_dir)
+	develop_method = get_develop_method(source_dir)
+	try:
+		func = develop_methods[develop_method]
+		return func(source_dir)
+	finally:
+		os.chdir(old_dir)
+
+def _run_packaging_develop(path):
+	dist = Distribution()
+	dist.parse_config_files()
+	try:
+		dist.run_command('develop_source')
+	except (IOError, os.error, PackagingError, CCompilerError) as msg:
+		raise SystemExit("error: " + str(msg))
+
+def _run_setuptools_develop(path): # check!!!
+	cmd = '%s setup.py develop --record=%s' # Note 5: check if there are other options should be supported?
+	record_file = os.path.join(path, 'RECORD')
+	os.system(cmd % (sys.executable, record_file))
+	if not os.path.exists(record_file):
+		raise ValueError('failed to install')
+	else:
+		egginfo_to_distinfo(record_file, remove_egginfo = True)
+
+# different develop methods
+develop_methods = {
+	'packaging': _run_packaging_develop,
+    'setuptools': _run_setuptools_develop}
\ No newline at end of file
diff -r fd6446a88fe3 -r aa68d35988bb Lib/packaging/run.py
--- a/Lib/packaging/run.py	Wed Jun 15 23:58:57 2011 +0200
+++ b/Lib/packaging/run.py	Thu Jun 16 17:15:53 2011 +0800
@@ -11,6 +11,7 @@
 from packaging.util import _is_archive_file, generate_setup_py
 from packaging.command import get_command_class, STANDARD_COMMANDS
 from packaging.install import install, install_local_project, remove
+from packaging.develop import develop_local_project
 from packaging.database import get_distribution, get_distributions
 from packaging.depgraph import generate_graph
 from packaging.fancy_getopt import FancyGetopt
@@ -70,6 +71,17 @@
 
 """
 
+develop_usage = """\
+Usage: pysetup develop [src_dir]
+   or: pysetup develop --help
+
+Deploy a project source in 'development mode'.
+
+positional arguments:
+   scr_dir  path to source directory
+
+"""
+
 metadata_usage = """\
 Usage: pysetup metadata [dist] [-f field ...]
    or: pysetup metadata [dist] [--all]
@@ -255,6 +267,21 @@
         else:
             return 1
 
+@action_help(develop_usage)
+def _develop(dispatcher, args, **kw):
+	# first check if we are in a source directory
+	if len(args) < 2:
+		# are we inside a project source dir?
+		listing = os.listdir(os.getcwd())
+		if 'setup.py' in listing or 'setup.cfg' in listing:
+			args.insert(1, os.getcwd())
+		else:
+			logger.warning('no project to deploy')
+			return
+	# installing from a source dir
+	if os.path.isdir(args[1]):
+		develop_local_project(args[1])
+
 
 @action_help(metadata_usage)
 def _metadata(dispatcher, args, **kw):
@@ -389,6 +416,7 @@
     ('run', 'Run one or several commands', _run),
     ('metadata', 'Display the metadata of a project', _metadata),
     ('install', 'Install a project', _install),
+    ('develop', 'Deploy a project source in development mode', _develop),
     ('remove', 'Remove a project', _remove),
     ('search', 'Search for a project in the indexes', _search),
     ('list', 'List installed releases', _list),