Updating ls_remote doc and enabling it via Git.ls_remote

README.md

@@ -153,6 +153,11 @@ Here are the operations that need read permission only.
     g.show()
     g.show('HEAD')
     g.show('v2.8', 'README.md')
+
+    Git.ls_remote('https://github.com/schacon/ruby-git.git') # returns a hash containing the available references of the repo.
+    Git.ls_remote('/path/to/local/repo')
+    Git.ls_remote() # same as Git.ls_remote('.')
+
 ```
 
 And here are the operations that will need to write to your git repository.

git.gemspec

@@ -29,6 +29,7 @@ Gem::Specification.new do |s|
     'lib/git.rb',
     'lib/git/author.rb',
     'lib/git/base.rb',
+    'lib/git/base/factory.rb',
     'lib/git/branch.rb',
     'lib/git/branches.rb',
     'lib/git/config.rb',

lib/git.rb

@@ -139,6 +139,15 @@ def self.global_config(name = nil, value = nil)
   def self.init(working_dir = '.', options = {})
     Base.init(working_dir, options)
   end
+
+  # returns a Hash containing information about the references 
+  # of the target repository
+  #
+  # @param [String|NilClass] location the target repository location or nil for '.'
+  # @return [{String=>Hash}] the available references of the target repo.
+  def self.ls_remote(location=nil)
+    Git::Lib.new.ls_remote(location)
+  end
 
   # open an existing git working directory
   # 

lib/git/lib.rb

@@ -393,6 +393,7 @@ def ls_files(location=nil)
     end
 
     def ls_remote(location=nil)
+      location ||= '.'
       Hash.new{ |h,k| h[k] = {} }.tap do |hsh|
         command_lines('ls-remote', [location], false).each do |line|
           (sha, info) = line.split("\t")