Remove dirty session tracking (it's too fragile)

I never liked this code and the additional complexity it introduced, so
lets try without for a while and see if anyone complains. If I really want
to I can always get the code back from version control.

Pull request #37: #37
Issue #38: #38

autoload/xolox/session.vim

@@ -1,9 +1,9 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: April 18, 2013
+" Last Change: April 20, 2013
 " URL: http://peterodding.com/code/vim/session/
 
-let g:xolox#session#version = '1.5.2'
+let g:xolox#session#version = '1.5.3'
 
 " Public API for session persistence. {{{1
 
@@ -263,7 +263,7 @@ endfunction
 function! xolox#session#auto_save() " {{{2
   if !v:dying && g:session_autosave != 'no'
     let name = s:get_name('', 0)
-    if name != '' && exists('s:session_is_dirty')
+    if name != ''
       let msg = "Do you want to save your editing session before quitting Vim?"
       if s:prompt(msg, 'g:session_autosave')
         execute 'SaveSession' fnameescape(name)
@@ -284,66 +284,6 @@ function! xolox#session#auto_unlock() " {{{2
   endwhile
 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
-  " session hasn't changed.
-  if v:this_session == ''
-    " Don't waste CPU time when no session is loaded.
-    return
-  elseif !exists('s:cached_layouts')
-    let s:cached_layouts = {}
-  else
-    " Clear non-existing tab pages from s:cached_layouts.
-    let last_tabpage = tabpagenr('$')
-    call filter(s:cached_layouts, 'v:key <= last_tabpage')
-  endif
-  " Check the buffer list.
-  let all_buffers = s:serialize_buffer_list()
-  if all_buffers != get(s:cached_layouts, 0, '')
-    let s:session_is_dirty = 1
-  endif
-  let s:cached_layouts[0] = all_buffers
-  " Check the layout of the current tab page.
-  let tabpagenr = tabpagenr()
-  let keys = ['tabpage:' . tabpagenr]
-  let buflist = tabpagebuflist()
-  for winnr in range(1, winnr('$'))
-    " Create a string that describes the state of the window {winnr}.
-    call add(keys, printf('width:%i,height:%i,buffer:%i',
-          \ winwidth(winnr), winheight(winnr), buflist[winnr - 1]))
-  endfor
-  let layout = join(keys, "\n")
-  if layout != get(s:cached_layouts, tabpagenr, '')
-    let s:session_is_dirty = 1
-  endif
-  let s:cached_layouts[tabpagenr] = layout
-endfunction
-
-function! s:serialize_buffer_list()
-  if &sessionoptions =~ '\<buffers\>'
-    return join(map(range(1, bufnr('$')), 's:serialize_buffer_state(v:val)'), "\n")
-  endif
-  return ''
-endfunction
-
-function! s:serialize_buffer_state(bufnr)
-  " TODO ssop =~ '\<blank\>' ?
-  let bufname = bufname(a:bufnr)
-  if bufname =~ '^NERD_tree_\d\+$'
-    " TODO I thought this would work, but somehow it doesn't?!
-    let root = getbufvar(a:bufnr, 'b:NERDTreeRoot')
-    if !empty(root)
-      let bufname = root.path.str() . '/' . bufname
-    endif
-  elseif bufname != ''
-    let bufname = fnamemodify(bufname, ':p')
-  endif
-  return a:bufnr . ':' . bufname
-endfunction
-
 " Commands that enable users to manage multiple sessions. {{{1
 
 function! s:prompt(msg, var)
@@ -372,7 +312,6 @@ function! xolox#session#open_cmd(name, bang) abort " {{{2
       let s:oldcwd = oldcwd
       call s:lock_session(path)
       execute 'source' fnameescape(path)
-      unlet! s:session_is_dirty
       call s:last_session_persist(name)
       call xolox#misc#timer#stop("session.vim %s: Opened %s session in %s.", g:xolox#session#version, string(name), starttime)
       call xolox#misc#msg#info("session.vim %s: Opened %s session from %s.", g:xolox#session#version, string(name), fnamemodify(path, ':~'))
@@ -414,7 +353,6 @@ function! xolox#session#save_cmd(name, bang) abort " {{{2
       call xolox#misc#msg#info("session.vim %s: Saved %s session to %s.", g:xolox#session#version, string(name), friendly_path)
       let v:this_session = path
       call s:lock_session(path)
-      unlet! s:session_is_dirty
     endif
   endif
 endfunction
@@ -441,7 +379,7 @@ endfunction
 
 function! xolox#session#close_cmd(bang, silent) abort " {{{2
   let name = s:get_name('', 0)
-  if name != '' && exists('s:session_is_dirty')
+  if name != ''
     let msg = "Do you want to save your current editing session before closing it?"
     if s:prompt(msg, 'g:session_autosave')
       SaveSession
@@ -470,7 +408,6 @@ function! xolox#session#close_cmd(bang, silent) abort " {{{2
     execute s:oldcwd
     unlet s:oldcwd
   endif
-  unlet! s:session_is_dirty
   if v:this_session == ''
     if !a:silent
       let msg = "session.vim %s: Closed session."

plugin/session.vim

@@ -1,6 +1,6 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: December 11, 2011
+" Last Change: April 20, 2013
 " URL: http://peterodding.com/code/vim/session/
 
 " Support for automatic update using the GLVS plug-in.
@@ -79,7 +79,6 @@ augroup PluginSession
   au VimEnter * nested call xolox#session#auto_load()
   au VimLeavePre * call xolox#session#auto_save()
   au VimLeavePre * call xolox#session#auto_unlock()
-  au BufEnter * call xolox#session#auto_dirty_check()
 augroup END
 
 " Define commands that enable users to manage multiple named sessions.