Add missing autocommands for filetype detection (#5)

Author: cmhamill

ftdetect/arcanist.vim

@@ -22,5 +22,8 @@
 autocmd BufNewFile,BufRead .arc{config,lint,rc,unit} setfiletype json
 
 let s:tmp = !empty($TMPDIR) ? '$TMPDIR' : '/tmp'
-execute 'au BufNewFile,BufRead ' . s:tmp . '/*/new-commit setfiletype arcanistdiff'
+execute 'au BufNewFile,BufRead ' . s:tmp . '/*/arcanist-patch-commit-message setfiletype arcanistdiff'
+execute 'au BufNewFile,BufRead ' . s:tmp . '/*/commit-message setfiletype arcanistdiff'
 execute 'au BufNewFile,BufRead ' . s:tmp . '/*/differential-edit-revision-info setfiletype arcanistdiff'
+execute 'au BufNewFile,BufRead ' . s:tmp . '/*/differential-update-comments setfiletype arcanistdiff'
+execute 'au BufNewFile,BufRead ' . s:tmp . '/*/new-commit setfiletype arcanistdiff'