Make :RestartVim preserve $VIM and $VIMRUNTIME (issue #9)

README.md

@@ -98,6 +98,10 @@ By default this option is set to `'prompt'`. When you've opened a session and yo
 
 By default this option is set to false (0). When you set this option to true (1) and you start Vim, the session plug-in will open your last used session instead of the default session. Note that the session plug-in will still show you the dialog asking whether you want to restore the last used session. To get rid of the dialog you have to set `g:session_autoload` to `'yes'`.
 
+### The `g:session_restart_environment` option
+
+This option is a list of environment variable names (without the dollar signs) that the `:RestartVim` command will pass on to the new instance of Vim. This option is only useful on UNIX. By default the three environment variables `$TERM`, `$VIM` and `$VIMRUNTIME` are included in this list.
+
 ### The `g:loaded_session` option
 
 This variable isn't really an option but if you want to avoid loading the `session.vim` plug-in you can set this variable to any value in your [vimrc script] [vimrc]:

autoload/xolox/session.vim

@@ -1,9 +1,9 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: September 28, 2011
+" Last Change: October 1, 2011
 " URL: http://peterodding.com/code/vim/session/
 
-let g:xolox#session#version = '1.4.19'
+let g:xolox#session#version = '1.4.20'
 
 " Public API for session persistence. {{{1
 
@@ -259,6 +259,7 @@ function! xolox#session#auto_unlock() " {{{2
 endfunction
 
 function! xolox#session#auto_dirty_check() " {{{2
+  " TODO Why execute this on every buffer change?! Instead execute it only when we want to know whether the session is dirty!
   " This function is called each time a BufEnter event fires to detect when
   " the current tab page (or the buffer list) is changed in some way. This
   " enables the plug-in to not bother with the auto-save dialog when the
@@ -461,6 +462,7 @@ endfunction
 
 function! xolox#session#restart_cmd(bang, args) abort " {{{2
   if !has('gui_running')
+    " In console Vim we can't start a new Vim and kill the old one...
     let msg = "session.vim %s: The :RestartVim command only works in graphical Vim!"
     call xolox#misc#msg#warn(msg, g:xolox#session#version)
   else
@@ -473,12 +475,16 @@ function! xolox#session#restart_cmd(bang, args) abort " {{{2
     if !empty(args)
       let command .= ' -c ' . shellescape(args)
     endif
-    if has('win32') || has('win64')
+    if xolox#misc#os#is_win()
       execute '!start' command
     else
-      let term = shellescape(fnameescape($TERM))
-      let encoding = "--cmd ':set enc=" . escape(&enc, '\ ') . "'"
-      silent execute '! TERM=' . term command encoding '&'
+      let cmdline = []
+      for variable in g:session_restart_environment
+        call add(cmdline, variable . '=' . shellescape(fnameescape(eval('$' . variable))))
+      endfor
+      call add(cmdline, command)
+      call add(cmdline, printf("--cmd ':set enc=%s'", escape(&enc, '\ ')))
+      silent execute '!' join(cmdline, ' ') '&'
     endif
     execute 'CloseSession' . a:bang
     silent quitall

doc/session.txt

@@ -188,6 +188,14 @@ instead of the default session. Note that the session plug-in will still show
 you the dialog asking whether you want to restore the last used session. To
 get rid of the dialog you have to set |g:session_autoload| to 'yes'.
 
+-------------------------------------------------------------------------------
+The *g:session_restart_environment* option
+
+This option is a list of environment variable names (without the dollar signs)
+that the |:RestartVim| command will pass on to the new instance of Vim. This
+option is only useful on UNIX. By default the three environment variables
+'$TERM', '$VIM' and '$VIMRUNTIME' are included in this list.
+
 -------------------------------------------------------------------------------
 The *g:loaded_session* option
 

plugin/session.vim

@@ -1,6 +1,6 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: September 28, 2011
+" Last Change: October 1, 2011
 " URL: http://peterodding.com/code/vim/session/
 
 " Support for automatic update using the GLVS plug-in.
@@ -34,6 +34,12 @@ if !exists('g:session_default_to_last')
   let g:session_default_to_last = 0
 endif
 
+" On UNIX the :RestartVim command will pass the following environment
+" variables on to the new instance of Vim.
+if !exists('g:session_restart_environment')
+  let g:session_restart_environment = ['TERM', 'VIM', 'VIMRUNTIME']
+endif
+
 " The default directory where session scripts are stored.
 if !exists('g:session_directory')
   if xolox#misc#os#is_win()