New option: g:startify_session_number

Closes #268.

autoload/startify.vim

@@ -568,6 +568,11 @@ endfunction
 
 " Function: s:show_sessions {{{1
 function! s:show_sessions() abort
+  let limit = get(g:, 'startify_session_number', 999) - 1
+  if limit <= -1
+    return
+  endif
+
   let sfiles = split(globpath(s:session_dir, '*'), '\n')
   let sfiles = filter(sfiles, 'v:val !~# "__LAST__$"')
   let sfiles = filter(sfiles,
@@ -601,6 +606,9 @@ function! s:show_sessions() abort
     endif
     call s:register(line('$'), index, 'session', 'SLoad', fname)
     let b:startify.entry_number += 1
+    if i == limit
+      break
+    endif
   endfor
 
   call append('$', '')

doc/startify.txt

@@ -114,6 +114,7 @@ default values.
     |g:startify_session_before_save|
     |g:startify_session_delete_buffers|
     |g:startify_session_dir|
+    |g:startify_session_number|
     |g:startify_session_persistence|
     |g:startify_session_remove_lines|
     |g:startify_session_savecmds|
@@ -460,6 +461,14 @@ Example:
            \ 'silent !pdfreader ~/latexproject/main.pdf &'
            \ ]
 <
+------------------------------------------------------------------------------
+                                                     *g:startify_session_number*
+>
+    let g:startify_session_number = 999
+<
+The maximum number of sessions to display. Makes the most sense together with
+|g:startify_session_sort|.
+
 ------------------------------------------------------------------------------
                                                        *g:startify_session_sort*
 >