Change view helper highlighting from "keyword" to "match"

The primary purpose of this change is to avoid false positives in hash
keywords, which vim-ruby currently handles, but at great cost.  View
helpers are a good place to try out this change as they're
autogenerated, and this change has the added bonus of simplifying the
handling of the "?" helpers.

References: vim-ruby/vim-ruby#452

Author: tpope

after/syntax/ruby/rails.vim

@@ -52,10 +52,10 @@ if s:path =~# '/app/jobs/.*\.rb$'
 endif
 
 if s:path =~# '/app/helpers/.*_helper\.rb$\|/app/views/'
-  syn keyword rubyViewHelper
+  let s:autogenerated_helpers = '
         \ action_name asset_path asset_url atom_feed audio_path audio_tag audio_url auto_discovery_link_tag
         \ button_tag button_to
-        \ cache cache_fragment_name cache_if cache_unless capture cdata_section check_box check_box_tag collection_check_boxes collection_radio_buttons collection_select color_field color_field_tag compute_asset_extname compute_asset_host compute_asset_path concat content_tag content_tag_for controller controller_name controller_path convert_to_model cookies csp_meta_tag csrf_meta_tag csrf_meta_tags current_cycle cycle
+        \ cache cache_fragment_name cache_if cache_unless capture cdata_section check_box check_box_tag collection_check_boxes collection_radio_buttons collection_select color_field color_field_tag compute_asset_extname compute_asset_host compute_asset_path concat content_for content_for? content_tag content_tag_for controller controller_name controller_path convert_to_model cookies csp_meta_tag csrf_meta_tag csrf_meta_tags current_cycle current_page? cycle
         \ date_field date_field_tag date_select datetime_field datetime_field_tag datetime_local_field datetime_local_field_tag datetime_select debug distance_of_time_in_words distance_of_time_in_words_to_now div_for dom_class dom_id
         \ email_field email_field_tag escape_javascript escape_once excerpt
         \ favicon_link_tag field_set_tag fields fields_for file_field file_field_tag flash font_path font_url form_for form_tag form_with
@@ -74,13 +74,14 @@ if s:path =~# '/app/helpers/.*_helper\.rb$\|/app/views/'
         \ url_field url_field_tag url_for url_to_asset url_to_audio url_to_font url_to_image url_to_javascript url_to_stylesheet url_to_video utf8_enforcer_tag
         \ video_path video_tag video_url
         \ week_field week_field_tag word_wrap
-  syn match rubyViewHelper '\<select\>\%(\s*{\|\s*do\>\|\s*(\=\s*&\)\@!'
-  syn match rubyViewHelper '\<\%(content_for\w\@!?\=\|current_page?\)'
-  syn match rubyViewHelper '\.\@<!\<\(h\|html_escape\|u\|url_encode\)\>'
-  syn match rubyViewHelper '\<\%(asset_pack_path\|image_pack_tag\|javascript_pack_tag\|stylesheet_pack_tag\)\>'
-  syn match rubyViewHelper '\<action_cable_meta_tag\>'
+        \'[1:-1]
+  exe 'syn match rubyViewHelper "\v<%(' . escape(tr(s:autogenerated_helpers, ' ', '|'), '?') . ')[[:keyword:]!?:]@!"'
+  syn match rubyViewHelper '\v<select>%([!?:]|\s*[{]|\s*do>|\s*[(]=\s*[&])@!'
+  syn match rubyViewHelper '\v\.@<!<%(h|html_escape|u|url_encode)>[!?:]@!'
+  syn match rubyViewHelper '\v<%(asset_pack_path|image_pack_tag|javascript_pack_tag|stylesheet_pack_tag)>[!?:]@!'
+  syn match rubyViewHelper '\v<action_cable_meta_tag>[!?:]@!'
   if s:path =~# '_[^\/]*$'
-    syn keyword rubyViewHelper local_assigns
+    syn match rubyViewHelper '\v<local_assigns>[!?:]@!'
   endif
 endif