fixes wrong echoing behavior on stock osx vim. resolves #209.

autoload/airline/extensions/hunks.vim

@@ -4,38 +4,43 @@
 let s:non_zero_only = get(g:, 'airline#extensions#hunks#non_zero_only', 0)
 let s:hunk_symbols = get(g:, 'airline#extensions#hunks#hunk_symbols', ['+', '~', '-'])
 
-let s:initialized = 0
-function! s:init()
-  if !s:initialized
-    let s:initialized = 1
-    if get(g:, 'loaded_signify', 0)
-      function! s:get_hunks()
+function! s:get_hunks_signify()
   let hunks = sy#repo#get_stats()
   if hunks[0] >= 0
     return hunks
   endif
   return []
 endfunction
-    elseif exists('*GitGutterGetHunkSummary')
-      function! s:get_hunks()
+
+function! s:get_hunks_gitgutter()
   if !get(g:, 'gitgutter_enabled', 0)
     return ''
   endif
   return GitGutterGetHunkSummary()
 endfunction
-    else
-      function! s:get_hunks()
-        return []
+
+function! s:get_hunks_empty()
+  return ''
 endfunction
+
+let s:source_func = ''
+function! s:get_hunks()
+  if empty(s:source_func)
+    if get(g:, 'loaded_signify', 0)
+      let s:source_func = 's:get_hunks_signify'
+    elseif exists('*GitGutterGetHunkSummary')
+      let s:source_func = 's:get_hunks_gitgutter'
+    else
+      let s:source_func = 's:get_hunks_empty'
     endif
   endif
+  return {s:source_func}()
 endfunction
 
 function! airline#extensions#hunks#get_hunks()
   if !get(w:, 'airline_active', 0)
     return ''
   endif
-  call <sid>init()
   let hunks = s:get_hunks()
   let string = ''
   if !empty(hunks)