add 'upload' arg to release script

so it can be used as a dry-run

tools/release

@@ -1,81 +1,85 b''
 #!/usr/bin/env python
 """IPython release script.
 
 This should ONLY be run at real release time.
 """
 from __future__ import print_function
 
 from toollib import *
 from gh_api import post_download
 
 # Get main ipython dir, this will raise if it doesn't pass some checks
 ipdir = get_ipdir()
 tooldir = pjoin(ipdir, 'tools')
 distdir = pjoin(ipdir, 'dist')
 
 # Where I keep static backups of each release
 ipbackupdir = os.path.expanduser('~/ipython/backup')
 if not os.path.exists(ipbackupdir):
     os.makedirs(ipbackupdir)
 
 # Start in main IPython dir
 cd(ipdir)
 
 # Load release info
 execfile(pjoin('IPython','core','release.py'), globals())
 # ensure js version is in sync
 sh('./setup.py jsversion')
 # build minified css and sourcemaps
 sh('./setup.py css -x -f')
 
 # Build site addresses for file uploads
 release_site = '%s/release/%s' % (archive, version)
 backup_site =  '%s/backup/' % archive
 
 # Start actual release process
 print()
 print('Releasing IPython')
 print('=================')
 print()
 print('Version:', version)
 print()
 print('Source IPython directory:', ipdir)
 print()
 
 # Perform local backup, go to tools dir to run it.
 cd(tooldir)
 sh('./make_tarball.py')
 sh('mv ipython-*.tgz %s' % ipbackupdir)
 
 # Build release files
 sh('./build_release %s' % ipdir)
 
+if 'upload' not in sys.argv:
+    print("`./release upload` to register and release")
+    sys.exit(0)
+
 # Register with the Python Package Index (PyPI)
 print( 'Registering with PyPI...')
 cd(ipdir)
 sh('./setup.py register')
 
 # Upload all files
 sh(sdists + ' upload')
 for py in ('2.7', '3.4'):
     sh('python%s setupegg.py bdist_wheel upload' % py)
 
 cd(distdir)
 print( 'Uploading distribution files...')
 
 for fname in os.listdir('.'):
     # TODO: update to GitHub releases API
     continue
     print('uploading %s to GitHub' % fname)
     desc = "IPython %s source distribution" % version
     post_download("ipython/ipython", fname, description=desc)
 
 # Make target dir if it doesn't exist
 sh('ssh %s "mkdir -p %s/release/%s" ' % (archive_user, archive_dir, version))
 sh('scp * %s' % release_site)
 
 print( 'Uploading backup files...')
 cd(ipbackupdir)
 sh('scp `ls -1tr *tgz | tail -1` %s' % backup_site)
 
 print('Done!')