provide a syntax check for eruby file

(cherry picked from commit e6ff3de83b9fee4f92dbc3042cf5fbcc48464f73)

syntax_checkers/eruby/eruby.vim

@@ -0,0 +1,54 @@
+"============================================================================
+"File:        eruby.vim
+"Description: Syntax checking plugin for syntastic.vim
+"Author:      Martin Grenfell <martin.grenfell at gmail dot com>
+"Modifier:    Grzegorz Smajdor <grzegorz.smajdor at gmail dot com>
+"License:     This program is free software. It comes without any warranty,
+"             to the extent permitted by applicable law. You can redistribute
+"             it and/or modify it under the terms of the Do What The Fuck You
+"             Want To Public License, Version 2, as published by Sam Hocevar.
+"             See http://sam.zoy.org/wtfpl/COPYING for more details.
+"============================================================================
+
+if exists("g:loaded_syntastic_eruby_ruby_checker")
+    finish
+endif
+let g:loaded_syntastic_eruby_ruby_checker=1
+
+if !exists("g:syntastic_ruby_exec")
+    let g:syntastic_ruby_exec = "ruby"
+endif
+
+function! SyntaxCheckers_eruby_ruby_IsAvailable()
+    return executable(expand(g:syntastic_ruby_exec))
+endfunction
+
+function! SyntaxCheckers_eruby_ruby_GetLocList()
+    let exe = expand(g:syntastic_ruby_exec)
+    if !has('win32')
+        let exe = 'RUBYOPT= ' . exe
+    endif
+
+    let fname = fnameescape(expand('%'))
+
+    let enc = &fileencoding != '' ? &fileencoding : &encoding
+    let encoding_string = enc ==# 'utf-8' ? ', :encoding => "UTF-8"' : ''
+
+    let makeprg =  'erb -xT - ' . shellescape(fnameescape(fname)) . ' \| ruby -c'
+
+    let errorformat =
+        \ '%-GSyntax OK,'.
+        \ '%E-:%l: syntax error\, %m,%Z%p^,'.
+        \ '%W-:%l: warning: %m,'.
+        \ '%Z%p^,'.
+        \ '%-C%.%#'
+
+    return SyntasticMake({
+        \ 'makeprg': makeprg,
+        \ 'errorformat': errorformat,
+        \ 'defaults': { 'bufnr': bufnr(""), 'vcol': 1 } })
+endfunction
+
+call g:SyntasticRegistry.CreateAndRegisterChecker({
+    \ 'filetype': 'eruby',
+    \ 'name': 'ruby'})