extract iminsert out of core into an extension

autoload/airline.vim

@@ -163,20 +163,12 @@ function! airline#update_highlight()
       let l:mode = ['insert']
     elseif l:m ==# "R"
       let l:mode = ['replace']
-    elseif l:m =~# '\v(v|V|)'
-      let l:mode = ['visual']
-    elseif l:m =~# '\v(s|S|)'
+    elseif l:m =~# '\v(v|V||s|S|)'
       let l:mode = ['visual']
     else
       let l:mode = ['normal']
     endif
     let g:airline_current_mode_text = get(g:airline_mode_map, l:m, l:m)
-    if g:airline_detect_iminsert && &iminsert
-      if get(g:, 'airline_powerline_fonts', 0)
-        let g:airline_current_mode_text .= ' '.g:airline_left_alt_sep
-      endif
-      let g:airline_current_mode_text .= ' '.toupper(get(b:, 'keymap_name', 'lang'))
-    endif
   else
     let l:mode = ['inactive']
   endif

autoload/airline/extensions.vim

@@ -139,6 +139,10 @@ function! airline#extensions#load()
     call airline#extensions#whitespace#init()
   endif
 
+  if g:airline_detect_iminsert
+    call airline#extensions#iminsert#init()
+  endif
+
   call airline#exec_funcrefs(g:airline_statusline_funcrefs, 0)
 endfunction
 

autoload/airline/extensions/iminsert.vim

@@ -0,0 +1,14 @@
+" MIT license. Copyright (c) 2013 Bailey Ling.
+" vim: ts=2 sts=2 sw=2 fdm=indent
+
+function! airline#extensions#iminsert#get_text()
+  if &iminsert
+    return toupper(get(b:, 'keymap_name', 'lang'))
+  endif
+  return ''
+endfunction
+
+function! airline#extensions#iminsert#init()
+  let g:airline_section_a .= ' '.g:airline_left_alt_sep.' %{airline#extensions#iminsert#get_text()}'
+endfunction
+