feat(): allow for buffer index formatting

autoload/airline/extensions/tabline/buffers.vim

@@ -13,8 +13,7 @@ let s:current_modified = 0
 let s:current_tabline = ''
 let s:current_visible_buffers = []
 
-let s:number_map = &encoding == 'utf-8'
-      \ ? {
+let s:number_map = {
       \ '0': '⁰',
       \ '1': '¹',
       \ '2': '²',
@@ -26,6 +25,8 @@ let s:number_map = &encoding == 'utf-8'
       \ '8': '⁸',
       \ '9': '⁹'
       \ }
+let s:number_map = &encoding == 'utf-8'
+      \ ? get(g:, 'airline#extensions#tabline#buffer_idx_format', s:number_map)
       \ : {}
 
 function! airline#extensions#tabline#buffers#off()

doc/airline.txt

@@ -566,8 +566,8 @@ with the middle mouse button to delete that buffer.
 
 * enable/disable displaying tab type (far right) >
   let g:airline#extensions#tabline#show_tab_type = 1
-  
-  Note: The tab-type will only be displayed in tab-mode, 
+
+  Note: The tab-type will only be displayed in tab-mode,
   if there are no splits shown. (See: g:airline#extensions#tabline#show_splits)
 
 * rename label for buffers (default: 'buffers') (c)
@@ -602,6 +602,21 @@ with the middle mouse button to delete that buffer.
   Use |gt| for switching tabs.
   In tabmode, those mappings will switch to the specified tab.
 
+* change the display format of the buffer index >
+  let g:airline#extensions#tabline#buffer_idx_format = {
+        \ '0': '0 ',
+        \ '1': '1 ',
+        \ '2': '2 ',
+        \ '3': '3 ',
+        \ '4': '4 ',
+        \ '5': '5 ',
+        \ '6': '6 ',
+        \ '7': '7 ',
+        \ '8': '8 ',
+        \ '9': '9 '
+        \}
+<
+
 * defines the name of a formatter for how buffer names are displayed. (c)
   let g:airline#extensions#tabline#formatter = 'default'