old_contents: #!/usr/bin/env python 
  
  # Display authors which appear as contributors in both (two) repositories.
  
  
  import os,sys
  
  def usage():
  	print 'Show authors which appear in two git repositories.'
  	print 'python2 git-author-comm.py [path-to-git-repo] [path-to-git-repo]'
  
  def sysout(command):
  	return os.popen(command).read()
  
  def get_authors(git):
  	cmd = "git --work-tree="+git+" --git-dir="+git+"/.git log --format='%aN' | sort -u"
  	# Split results to a list.
  	authors = sysout(cmd).split('\n')
  	# Remove any empty lines prior to return.
  	return filter(None, authors)
  
  def get_same_authors(a1,a2):
  	# Return a set of authors which appear in both repositories.
  	return set(a1).intersection(a2)
  
  if __name__ == "__main__":
  	if len(sys.argv) != 3:
  		usage()
  	else:
  		git1 = sys.argv[1]
  		git2 = sys.argv[2]
  		
  		authors = get_same_authors(get_authors(git1),get_authors(git2))
  		if len(authors) == 0:
  			print 'There are no matches.'
  		else:
  			print 'The folowing appear in both repositories: '
  			for author in authors:
  				print author
  					
new_contents: #!/usr/bin/env python 
  
  # Display authors which appear as contributors in both (two) repositories.
  
  
  import os,sys
  
  def usage():
  	print 'Show authors which appear in two local git repositories.'
  	print 'python2 git-author-comm.py [path-to-local-git-repo] [path-to-local-git-repo]'
  
  def sysout(command):
  	return os.popen(command).read()
  
  def get_authors(git):
  	cmd = "git --work-tree="+git+" --git-dir="+git+"/.git log --format='%aN' | sort -u"
  	# Split results to a list.
  	authors = sysout(cmd).split('\n')
  	# Remove any empty lines prior to return.
  	return filter(None, authors)
  
  def get_same_authors(a1,a2):
  	# Return a set of authors which appear in both repositories.
  	return set(a1).intersection(a2)
  
  if __name__ == "__main__":
  	if len(sys.argv) != 3:
  		usage()
  	else:
  		git1 = sys.argv[1]
  		git2 = sys.argv[2]
  		
  		authors = get_same_authors(get_authors(git1),get_authors(git2))
  		if len(authors) == 0:
  			print 'There are no matches.'
  		else:
  			print 'The folowing appear in both repositories: '
  			for author in authors:
  				print author
  					
subject: Make it more obvious that you need to use a local repository as an argument, not a url