title: "bundle install" fails when setting :git path in Gemfile
body: <p>I want to update one of my gems from the master source branch instead of from a gem repo. So I put this in my Gemfile:</p>
  
  <pre><code>gem "prawn", :git =&gt; "https://github.com/sandal/prawn.git"
  </code></pre>
  
  <p>However, now when I run:</p>
  
  <pre><code>bundle install
  </code></pre>
  
  <p>or:</p>
  
  <pre><code>bundle update
  </code></pre>
  
  <p>I get:</p>
  
  <pre><code>Updating https://github.com/sandal/prawn.git
  syntax error on line 42, col 0: `end'
  /Users/me/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/yaml.rb:137:in `load': undefined method `path' for #&lt;String:0x101aa83c0&gt; (NoMethodError)
  from /Users/me/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/specification.rb:480:in `from_yaml'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler.rb:238:in `load_gemspec'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler.rb:235:in `chdir'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler.rb:235:in `load_gemspec'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/source.rb:353:in `load_spec_files'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/source.rb:352:in `each'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/source.rb:352:in `load_spec_files'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/source.rb:570:in `load_spec_files'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/source.rb:385:in `local_specs'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/source.rb:555:in `specs'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/definition.rb:356:in `converge_locked_specs'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/definition.rb:345:in `each'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/definition.rb:345:in `converge_locked_specs'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/definition.rb:143:in `resolve'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/definition.rb:90:in `specs'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/definition.rb:85:in `resolve_remotely!'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/installer.rb:43:in `run'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/installer.rb:8:in `install'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/cli.rb:219:in `install'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/vendor/thor/task.rb:22:in `send'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/vendor/thor/task.rb:22:in `run'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/vendor/thor/invocation.rb:118:in `invoke_task'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/vendor/thor.rb:263:in `dispatch'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/lib/bundler/vendor/thor/base.rb:386:in `start'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/bundler-1.0.20/bin/bundle:13
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/bin/bundle:19:in `load'
  from /Users/me/.rvm/gems/ree-1.8.7-2011.03@myapp/bin/bundle:19
  </code></pre>
  
  <p>Any ideas on how I can fix this?</p>