make branch/bufferline default statusline rather than overrides

autoload/airline/extensions/branch.vim

@@ -1,19 +1,14 @@
 " MIT license. Copyright (c) 2013 Bailey Ling.
 " vim: ts=2 sts=2 sw=2 fdm=indent
 
-function! airline#extensions#branch#apply()
-  if exists('w:airline_left_only')
-    return
-  endif
-  let w:airline_section_b =
-        \ exists('*fugitive#head') && strlen(fugitive#head()) > 0
-          \ ? g:airline_branch_prefix.fugitive#head()
-          \ : exists('*lawrencium#statusline') && strlen(lawrencium#statusline()) > 0
-            \ ? g:airline_branch_prefix.lawrencium#statusline()
-            \ : ''
-endfunction
-
 function! airline#extensions#branch#init(ext)
-  call a:ext.add_statusline_funcref(function('airline#extensions#branch#apply'))
+  if g:airline_section_b == ''
+    let g:airline_section_b =
+          \ exists('*fugitive#head') && strlen(fugitive#head()) > 0
+            \ ? g:airline_branch_prefix.fugitive#head()
+            \ : exists('*lawrencium#statusline') && strlen(lawrencium#statusline()) > 0
+              \ ? g:airline_branch_prefix.lawrencium#statusline()
+              \ : ''
+  endif
 endfunction
 

autoload/airline/extensions/bufferline.vim

@@ -1,13 +1,6 @@
 " MIT license. Copyright (c) 2013 Bailey Ling.
 " vim: ts=2 sts=2 sw=2 fdm=indent
 
-function! airline#extensions#bufferline#apply()
-  if exists('w:airline_left_only')
-    return
-  endif
-  let w:airline_section_c = '%{bufferline#refresh_status()}'.bufferline#get_status_string()
-endfunction
-
 function! airline#extensions#bufferline#init(ext)
   highlight AlBl_active gui=bold cterm=bold term=bold
   highlight link AlBl_inactive Al6
@@ -17,5 +10,7 @@ function! airline#extensions#bufferline#init(ext)
   let g:bufferline_active_buffer_right = ''
   let g:bufferline_separator = ' '
 
-  call a:ext.add_statusline_funcref(function('airline#extensions#bufferline#apply'))
+  if g:airline_section_c == '%f%m'
+    let g:airline_section_c = '%{bufferline#refresh_status()}'.bufferline#get_status_string()
+  endif
 endfunction

autoload/airline/extensions/syntastic.vim

@@ -1,12 +1,8 @@
 " MIT license. Copyright (c) 2013 Bailey Ling.
 " vim: ts=2 sts=2 sw=2 fdm=indent
 
-function! airline#extensions#syntastic#apply()
-  let w:airline_section_gutter = '%#warningmsg#%{SyntasticStatuslineFlag()}'
-endfunction
-
 function! airline#extensions#syntastic#init(ext)
-  if g:airline_enable_syntastic && exists('*SyntasticStatuslineFlag')
-    call a:ext.add_statusline_funcref(function('airline#extensions#syntastic#apply'))
+  if g:airline_section_gutter == ''
+    let g:airline_section_gutter = '%#warningmsg#%{SyntasticStatuslineFlag()}'
   endif
 endfunction