tabline: allow to show current buffer/tab at first position

This will make highlighting more consistent. Always first item is the
one where the cursor is.

autoload/airline/extensions/tabline/buffers.vim

@@ -111,6 +111,12 @@ endfunction
 function! s:get_visible_buffers()
   let buffers = airline#extensions#tabline#buflist#list()
   let cur = bufnr('%')
+  if get(g:, 'airline#extensions#tabline#current_first', 0)
+    if index(buffers, cur) > -1
+      call remove(buffers, index(buffers, cur))
+    endif
+    let buffers = [cur] + buffers
+  endif
 
   let total_width = 0
   let max_width = 0

autoload/airline/extensions/tabline/tabs.vim

@@ -43,7 +43,15 @@ function! airline#extensions#tabline#tabs#get()
   let b = airline#extensions#tabline#new_builder()
 
   call airline#extensions#tabline#add_label(b, 'tabs')
-  for i in range(1, tabpagenr('$'))
+  " always have current tabpage first
+  let tablist = range(1, tabpagenr('$'))
+  if get(g:, 'airline#extensions#tabline#current_first', 0)
+    if index(tablist, curtab) > -1
+      call remove(tablist, index(tablist, curtab))
+    endif
+    let tablist = [curtab] + tablist
+  endif
+  for i in tablist
     if i == curtab
       let group = 'airline_tabsel'
       if g:airline_detect_modified

doc/airline.txt

@@ -698,6 +698,10 @@ with the middle mouse button to delete that buffer.
 * rename label for tabs (default: 'tabs') (c) >
   let g:airline#extensions#tabline#tabs_label = 't'
 
+* always show current tabpage/buffer first >
+  let airline#extensions#tabline#current_first = 1
+<  default: 0
+
 * enable/disable displaying index of the buffer.
 
   When enabled, numbers will be displayed in the tabline and mappings will be