fix `am` command when given URLs that include the fragment

lib/hub/commands.rb

@@ -368,10 +368,12 @@ module Hub
       if url = args.find { |a| a =~ %r{^https?://(gist\.)?github\.com/} }
         idx = args.index(url)
         gist = $1 == 'gist.'
+        # strip the fragment part of the url
+        url.sub!(/#.+/, '')
         # strip extra path from "pull/42/files", "pull/42/commits"
-        url = url.sub(%r{(/pull/\d+)/\w*$}, '\1') unless gist
+        url.sub!(%r{(/pull/\d+)/\w*$}, '\1') unless gist
         ext = gist ? '.txt' : '.patch'
-        url += ext unless File.extname(url) == ext
+        url << ext unless File.extname(url) == ext
         patch_file = File.join(ENV['TMPDIR'] || '/tmp', "#{gist ? 'gist-' : ''}#{File.basename(url)}")
         args.before 'curl', ['-#LA', "hub #{Hub::Version}", url, '-o', patch_file]
         args[idx] = patch_file

test/hub_test.rb

@@ -461,7 +461,7 @@ class HubTest < Test::Unit::TestCase
     with_tmpdir('/tmp/') do
       assert_commands "curl -#LA 'hub #{Hub::Version}' https://github.com/defunkt/hub/pull/55.patch -o /tmp/55.patch",
                       "git am --signoff /tmp/55.patch -p2",
-                      "am --signoff https://github.com/defunkt/hub/pull/55 -p2"
+                      "am --signoff https://github.com/defunkt/hub/pull/55#comment_123 -p2"
 
       cmd = Hub("am https://github.com/defunkt/hub/pull/55/files").command
       assert_includes '/pull/55.patch', cmd