Fix API 422 error: `Duplicate value for "description"`

When looking up an existing hub token among user's authorizations, be
sure to fetch all results by following pagination links. Previously we
just stopped at the 1st page, and if the token for hub didn't appear
there we would try to create it, which would result in a 422 validation
error if it already existed.

References 1e4477b5

Fixes #531, fixes #558, fixes #563

features/authentication.feature

@@ -88,6 +88,40 @@ Feature: OAuth authentication
     And the exit status should be 0
     And the file "../home/.config/hub" should contain "oauth_token: OTOKEN"
 
+  Scenario: Re-use existing authorization found on page 3
+    Given the GitHub API server:
+      """
+      get('/authorizations') {
+        assert_basic_auth 'mislav', 'kitty'
+        page = (params[:page] || 1).to_i
+        if page < 3
+          response.headers['Link'] = %(<#{url}?page=#{page+1}>; rel="next")
+          json []
+        else
+          json [
+            {:token => 'OTOKEN', :note => 'hub', :note_url => 'http://hub.github.com/'}
+          ]
+        end
+      }
+      post('/authorizations') {
+        status 422
+        json :message => "Validation Failed",
+          :errors => [{:resource => "OauthAccess", :code => "already_exists", :field => "description"}]
+      }
+      get('/user') {
+        json :login => 'mislav'
+      }
+      post('/user/repos') {
+        json :full_name => 'mislav/dotfiles'
+      }
+      """
+    When I run `hub create` interactively
+    When I type "mislav"
+    And I type "kitty"
+    Then the output should contain "github.com password for mislav (never stored):"
+    And the exit status should be 0
+    And the file "../home/.config/hub" should contain "oauth_token: OTOKEN"
+
   Scenario: Credentials from GITHUB_USER & GITHUB_PASSWORD
     Given the GitHub API server:
       """

lib/hub/github_api.rb

@@ -192,12 +192,33 @@ module Hub
             end
           end.compact if data['errors']
         end
+        def links
+          @links ||= self['link'].to_s.scan(/<(.+?)>; rel="(.+?)"/).inject({}) do |map, (url, rel)|
+            map.update(rel.to_sym => URI.parse(url))
+          end
+        end
+        def next_url() links[:next] end
       end
 
       def get url, &block
         perform_request url, :Get, &block
       end
 
+      def get_all url, &block
+        previous_res = nil
+        user = url.user
+        while url
+          res = get(url, &block)
+          if url = res.next_url
+            url = url.dup
+            url.user = user
+          end
+          res.data.unshift(*previous_res.data) if res.success? && previous_res
+          previous_res = res
+        end
+        res
+      end
+
       def post url, params = nil
         perform_request url, :Post do |req|
           if params
@@ -299,7 +320,7 @@ module Hub
 
     module OAuth
       def apply_authentication req, url
-        if req.path =~ %r{^(/api/v3)?/authorizations$}
+        if req.path =~ %r{^(/api/v3)?/authorizations\b}
           super
         else
           user = url.user ? CGI.unescape(url.user) : config.username(url.host)
@@ -317,7 +338,7 @@ module Hub
         post(auth_url) if !two_factor_code
 
         # first try to fetch existing authorization
-        res = get(auth_url) do |req|
+        res = get_all(auth_url) do |req|
           req['X-GitHub-OTP'] = two_factor_code if two_factor_code
         end
         unless res.success?