Add hub merge command

It does what GitHub's "Merge pull request" button does:
merges the pull request with a nice commit message that
includes the pull request ID and title. Like `hub checkout`,
it creates a remote, but it does not create a local branch.

lib/hub/commands.rb

@@ -360,6 +360,34 @@ def checkout(args)
       end
     end
 
+    # $ git merge https://github.com/defunkt/hub/pull/73
+    # > git remote add -f -t feature git://github:com/mislav/hub.git
+    # > git merge mislav/feature --no-ff -m 'Merge pull request #73 from mislav/feature...'
+    def merge(args)
+      _, url_arg, new_branch_name = args.words
+      if url = resolve_github_url(url_arg) and url.project_path =~ /^pull\/(\d+)/
+        pull_id = $1
+        pull_data = api_client.pullrequest_info(url.project, pull_id)
+
+        args.delete new_branch_name
+        user, branch = pull_data['head']['label'].split(':', 2)
+        abort "Error: #{user}'s fork is not available anymore" unless pull_data['head']['repo']
+
+        if remotes.include? user
+          args.before ['remote', 'set-branches', '--add', user, branch]
+          args.before ['fetch', user, "+refs/heads/#{branch}:refs/remotes/#{user}/#{branch}"]
+        else
+          url = github_project(url.project_name, user).git_url(:private => pull_data['head']['repo']['private'],
+                                                               :https => https_protocol?)
+          args.before ['remote', 'add', '-f', '-t', branch, user, url]
+        end
+        idx = args.index url_arg
+        args.delete_at idx
+        args.insert idx, "#{user}/#{branch}", '--no-ff', '-m',
+                    "Merge pull request ##{pull_id} from #{user}/#{branch}\n\n#{pull_data['title']}"
+      end
+    end
+
     # $ git cherry-pick http://github.com/mislav/hub/commit/a319d88#comments
     # > git remote add -f mislav git://github.com/mislav/hub.git
     # > git cherry-pick a319d88

man/hub.1

@@ -96,6 +96,10 @@ Adds missing remote(s) with \fBgit remote add\fR prior to fetching\. New remotes
 Checks out the head of the pull request as a local branch, to allow for reviewing, rebasing and otherwise cleaning up the commits in the pull request before merging\. The name of the local branch can explicitly be set with \fIBRANCH\fR\.
 .
 .TP
+\fBgit merge\fR \fIPULLREQ\-URL\fR
+Merge the pull request with a nice commit message that includes the pull request ID and title\. Adds a remote but not a local branch\.
+.
+.TP
 \fBgit cherry\-pick\fR \fIGITHUB\-REF\fR
 Cherry\-pick a commit from a fork using either full URL to the commit or GitHub\-flavored Markdown notation, which is \fBuser@sha\fR\. If the remote doesn\'t yet exist, it will be added\. A \fBgit fetch <user>\fR is issued prior to the cherry\-pick attempt\.
 .

man/hub.1.ronn

@@ -73,6 +73,10 @@ hub enhances various git commands to ease most common workflows with GitHub.
     request before merging. The name of the local branch can explicitly be
     set with <BRANCH>.
 
+  * `git merge` <PULLREQ-URL>:
+    Merge the pull request with a nice commit message that includes the pull
+    request ID and title. Adds a remote but not a local branch.
+
   * `git cherry-pick` <GITHUB-REF>:
     Cherry-pick a commit from a fork using either full URL to the commit
     or GitHub-flavored Markdown notation, which is `user@sha`. If the remote

test/hub_test.rb

@@ -568,6 +568,40 @@ def test_checkout_pullrequest_existing_remote
       "checkout https://github.com/defunkt/hub/pull/73/files"
   end
 
+  def test_merge_no_changes
+    assert_forwarded "merge master"
+  end
+
+  def test_merge_pullrequest
+    stub_request(:get, "https://api.github.com/repos/defunkt/hub/pulls/73").
+      to_return(:body => mock_pull_response('blueyed:feature'))
+
+    assert_commands "git remote add -f -t feature blueyed git://github.com/blueyed/hub.git",
+      "git merge blueyed/feature --no-ff -m 'Merge pull request #73 from blueyed/feature\n\nMake eyes blue'",
+      "merge https://github.com/defunkt/hub/pull/73/files"
+  end
+
+  def test_merge_private_pullrequest
+    stub_request(:get, "https://api.github.com/repos/defunkt/hub/pulls/73").
+      to_return(:body => mock_pull_response('blueyed:feature', :private))
+
+    assert_commands "git remote add -f -t feature blueyed git@github.com:blueyed/hub.git",
+      "git merge blueyed/feature --no-ff -m 'Merge pull request #73 from blueyed/feature\n\nMake eyes blue'",
+      "merge https://github.com/defunkt/hub/pull/73/files"
+  end
+
+  def test_merge_pullrequest_existing_remote
+    stub_command_output 'remote', "origin\nblueyed"
+
+    stub_request(:get, "https://api.github.com/repos/defunkt/hub/pulls/73").
+      to_return(:body => mock_pull_response('blueyed:feature'))
+
+    assert_commands "git remote set-branches --add blueyed feature",
+      "git fetch blueyed +refs/heads/feature:refs/remotes/blueyed/feature",
+      "git merge blueyed/feature --no-ff -m 'Merge pull request #73 from blueyed/feature\n\nMake eyes blue'",
+      "merge https://github.com/defunkt/hub/pull/73/files"
+  end
+
   def test_version
     out = hub('--version')
     assert_includes "git version 1.7.0.4", out
@@ -967,7 +1001,7 @@ def mock_pull_response(label, priv = false)
       Hub::JSON.generate :head => {
         :label => label,
         :repo => {:private => !!priv}
-      }
+      }, :title => "Make eyes blue"
     end
 
     def improved_help_text