Update recently used files on the fly

Startify depends on v:oldfiles which lists recently used files (taken from the
viminfo file). But viminfo only gets updated once in a session: at exiting
Vim. Thus when you worked in a Vim instance for some time and opened multiple
new buffers, v:oldfiles (and therefore :Startify) wouldn't show the most
recently used files anymore.

Luckily v:oldfiles is editable, so now, each new buffer simply prepends its
associated filename to it, making :Startify always up-to-date.

References #148.

doc/startify.txt

@@ -385,7 +385,7 @@ A hardcoded example:
             \ ]
 <
 
-Also have a look at |startify-faq-09|.
+Also have a look at |startify-faq-08|.
 
 ------------------------------------------------------------------------------
                                                       *g:startify_custom_footer*
@@ -520,15 +520,13 @@ FAQ                                                               *startify-faq*
 
     |startify-faq-01|  I don't want the start screen to use cursorline!
     |startify-faq-02|  Recent files aren't shown!
-    |startify-faq-03|  Most recently used files don't seem to get updated
-                     at :Startify!
-    |startify-faq-04|  I have broken colors when using sessions!
-    |startify-faq-05|  How to disable common but unimportant files?
-    |startify-faq-06|  CtrlP or NERDTree open a split in Startify!
-    |startify-faq-07|  How do I get both NERDTree and Startify working at
+    |startify-faq-03|  I have broken colors when using sessions!
+    |startify-faq-04|  How to disable common but unimportant files?
+    |startify-faq-05|  CtrlP or NERDTree open a split in Startify!
+    |startify-faq-06|  How do I get both NERDTree and Startify working at
                      startup?
-    |startify-faq-08|  The session autoload feature is not working!
-    |startify-faq-09|  How do I center my header/footer?
+    |startify-faq-07|  The session autoload feature is not working!
+    |startify-faq-08|  How do I center my header/footer?
 
 ------------------------------------------------------------------------------
                                                                *startify-faq-01*
@@ -565,12 +563,6 @@ exactly.
 
 ------------------------------------------------------------------------------
                                                                *startify-faq-03*
-Most recently used files don't seem to get updated at :Startify!~
-
-Vim loads the list from viminfo only once, at startup.
-
-------------------------------------------------------------------------------
-                                                               *startify-faq-04*
 I have broken colors when using sessions!~
 
 Nothing this plugin could do about. Try playing around with 'sessionoptions'.
@@ -583,7 +575,7 @@ Some people swear it works for them with these settings:
     set sessionoptions=blank,curdir,folds,help,tabpages,winpos
 <
 ------------------------------------------------------------------------------
-                                                               *startify-faq-05*
+                                                               *startify-faq-04*
 How to disable common but unimportant files?~
 
 Use the skiplist. Personally I use:
@@ -596,7 +588,7 @@ Use the skiplist. Personally I use:
            \ ]
 <
 ------------------------------------------------------------------------------
-                                                               *startify-faq-06*
+                                                               *startify-faq-05*
 CtrlP or NERDTree open a split in Startify!~
 
 Put this in your vimrc:
@@ -609,7 +601,7 @@ solution:
     let g:ctrlp_reuse_window = 'startify'
 <
 ------------------------------------------------------------------------------
-                                                               *startify-faq-07*
+                                                               *startify-faq-06*
 How do I get both NERDTree and Startify working at startup?~
 
 Put this in your vimrc:
@@ -622,7 +614,7 @@ Put this in your vimrc:
                 \ | endif
 <
 ------------------------------------------------------------------------------
-                                                               *startify-faq-08*
+                                                               *startify-faq-07*
 The session autoload feature is not working!~
 
 Do you have NERDTree installed by any chance? If so, try this:
@@ -630,7 +622,7 @@ Do you have NERDTree installed by any chance? If so, try this:
     let NERDTreeHijackNetrw = 0
 <
 ------------------------------------------------------------------------------
-                                                               *startify-faq-09*
+                                                               *startify-faq-08*
 How do I center my header/footer?~
 
 Try something along these lines:

plugin/startify.vim

@@ -12,25 +12,32 @@ let g:loaded_startify = 1
 
 augroup startify
   if !get(g:, 'startify_disable_at_vimenter')
-    autocmd VimEnter * nested
-          \   if !argc() && (line2byte('$') == -1) && (v:progname =~? '^[-gmnq]\=vim\=x\=\%[\.exe]$')
-          \ |   if get(g:, 'startify_session_autoload') && filereadable('Session.vim')
-          \ |     source Session.vim
-          \ |   else
-          \ |     call startify#insane_in_the_membrane()
-          \ |   endif
-          \ | endif
-          \ | autocmd! startify VimEnter
+    autocmd VimEnter * nested call s:genesis()
   endif
 
   if get(g:, 'startify_session_persistence')
-    autocmd startify VimLeave *
-          \   if exists('v:this_session') && filewritable(v:this_session)
-          \ |   call startify#session_write(fnameescape(v:this_session))
-          \ | endif
+    autocmd VimLeave * call s:extinction()
   endif
 augroup END
 
+function! s:genesis()
+  if !argc() && (line2byte('$') == -1) && (v:progname =~? '^[-gmnq]\=vim\=x\=\%[\.exe]$')
+    if get(g:, 'startify_session_autoload') && filereadable('Session.vim')
+      source Session.vim
+    else
+      call startify#insane_in_the_membrane()
+    endif
+  endif
+  autocmd startify BufRead * if exists('v:oldfiles') | call insert(v:oldfiles, expand('<afile>'), 0) | endif
+  autocmd! startify VimEnter
+endfunction
+
+function! s:extinction()
+  if exists('v:this_session') && filewritable(v:this_session)
+    call startify#session_write(fnameescape(v:this_session))
+  endif
+endfunction
+
 command! -nargs=? -bar -complete=customlist,startify#session_list SSave   call startify#session_save(<f-args>)
 command! -nargs=? -bar -complete=customlist,startify#session_list SLoad   call startify#session_load(<f-args>)
 command! -nargs=? -bar -complete=customlist,startify#session_list SDelete call startify#session_delete(<f-args>)