add deprecation warnings.

autoload/airline/deprecation.vim

@@ -0,0 +1,21 @@
+" MIT License. Copyright (c) 2013 Bailey Ling.
+" vim: et ts=2 sts=2 sw=2
+
+function! airline#deprecation#check()
+  if exists('g:airline_enable_fugitive') || exists('g:airline_fugitive_prefix')
+    echom 'The g:airline_enable_fugitive and g:airline_fugitive_prefix variables are obsolete. Please read the documentation about the branch extension.'
+  endif
+
+  let tests = [
+        \ [ 'g:airline_paste_symbol', 'g:airline_symbols.paste' ],
+        \ [ 'g:airline_readonly_symbol', 'g:airline_symbols.readonly' ],
+        \ [ 'g:airline_linecolumn_prefix', 'g:airline_symbols.linenr' ],
+        \ [ 'g:airline_branch_prefix', 'g:airline_symbols.branch' ],
+        \ ]
+  for test in tests
+    if exists(test[0])
+      echom printf('The variable %s is deprecated and may not work in the future. It has been replaced with %s', test[0], test[1])
+    endif
+  endfor
+endfunction
+

autoload/airline/extensions.vim

@@ -195,8 +195,8 @@ function! airline#extensions#load()
 
   " load all other extensions not part of the default distribution
   for file in split(globpath(&rtp, "autoload/airline/extensions/*.vim"), "\n")
-    " check to see that both the resolved and unresolved paths do not match
+    " we have to check both resolved and unresolved paths, since it's possible
-    " up with the path of the found extension
+    " that they might not get resolved properly (see #187)
     if stridx(resolve(fnamemodify(file, ':p')), s:script_path) < 0
           \ && stridx(fnamemodify(file, ':p'), s:script_path) < 0
       let name = fnamemodify(file, ':t:r')

plugin/airline.vim

@@ -6,16 +6,14 @@ if &cp || v:version < 702 || (exists('g:loaded_airline') && g:loaded_airline)
 endif
 let g:loaded_airline = 1
 
+" autocmd VimEnter * call airline#deprecation#check()
+
 function! s:check_defined(variable, default)
   if !exists(a:variable)
     let {a:variable} = a:default
   endif
 endfunction
 
-if exists('g:airline_enable_fugitive') || exists('g:airline_fugitive_prefix')
-  echom 'The g:airline_enable_fugitive and g:airline_fugitive_prefix variables are obsolete. Please read the documentation about the branch extension.'
-endif
-
 call s:check_defined('g:airline_left_sep', get(g:, 'airline_powerline_fonts', 0)?"":">")
 call s:check_defined('g:airline_left_alt_sep', get(g:, 'airline_powerline_fonts', 0)?"":">")
 call s:check_defined('g:airline_right_sep', get(g:, 'airline_powerline_fonts', 0)?"":"<")