contrib: state explicitly how hgtest.vim can be installed

contrib/vim/hgtest.vim

@@ -1,41 +1,42
 " Vim syntax file
 " Language: Mercurial unified tests
 " Author: Steve Losh ([e-mail])
 "
-" Add the following line to your ~/.vimrc to enable:
+" Place this file in ~/.vim/syntax/ and add the following line to your
+" ~/.vimrc to enable:
 " au BufNewFile,BufRead *.t set filetype=hgtest
 "
 " If you want folding you'll need the following line as well:
 " let hgtest_fold=1
 "
 " You might also want to set the starting foldlevel for hgtest files:
 " autocmd Syntax hgtest setlocal foldlevel=1
 
 if exists("b:current_syntax")
   finish
 endif
 
 syn include @Shell syntax/sh.vim
 
 syn match hgtestComment /^[^ ].*$/
 syn region hgtestOutput start=/^  [^$>]/ start=/^  $/ end=/\v.(\n\n*[^ ])\@=/me=s end=/^  [$>]/me=e-3 end=/^$/ fold containedin=hgtestBlock
 syn match hgtestCommandStart /^  \$ / containedin=hgtestCommand
 syn region hgtestCommand start=/^  \$ /hs=s+4,rs=s+4 end=/^  [^>]/me=e-3 end=/^  $/me=e-2 containedin=hgtestBlock contains=@Shell keepend
 syn region hgtestBlock start=/^  /ms=e-2 end=/\v.(\n\n*[^ ])\@=/me=s end=/^$/me=e-1 fold keepend
 
 hi link hgtestCommandStart Keyword
 hi link hgtestComment Normal
 hi link hgtestOutput Comment
 
 if exists("hgtest_fold")
   setlocal foldmethod=syntax
 endif
 
 syn sync match hgtestSync grouphere NONE "^$"
 syn sync maxlines=200
 
 " It's okay to set tab settings here, because an indent of two spaces is specified
 " by the file format.
 setlocal tabstop=2 softtabstop=2 shiftwidth=2 expandtab
 
 let b:current_syntax = "hgtest"