check guard for all extensions. resolves #241.

autoload/airline/extensions/branch.vim

@@ -1,14 +1,18 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
-let s:empty_message = get(g:, 'airline#extensions#branch#empty_message',
-      \ get(g:, 'airline_branch_empty_message', ''))
-let s:symbol = get(g:, 'airline#extensions#branch#symbol', g:airline_symbols.branch)
-
 let s:has_fugitive = exists('*fugitive#head')
 let s:has_fugitive_detect = exists('*fugitive#detect')
 let s:has_lawrencium = exists('*lawrencium#statusline')
 
+if !s:has_fugitive && !s:has_lawrencium
+  finish
+endif
+
+let s:empty_message = get(g:, 'airline#extensions#branch#empty_message',
+      \ get(g:, 'airline_branch_empty_message', ''))
+let s:symbol = get(g:, 'airline#extensions#branch#symbol', g:airline_symbols.branch)
+
 function! airline#extensions#branch#get_head()
   let head = ''
 

autoload/airline/extensions/bufferline.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !exists('*bufferline#get_status_string')
+  finish
+endif
+
 let s:overwrite = get(g:, 'airline#extensions#bufferline#overwrite_variables', 1)
 
 function! airline#extensions#bufferline#init(ext)

autoload/airline/extensions/commandt.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !get(g:, 'command_t_loaded', 0)
+  finish
+endif
+
 function! airline#extensions#commandt#apply(...)
   if bufname('%') ==# 'GoToFile'
     call airline#extensions#apply_left_override('CommandT', '')

autoload/airline/extensions/csv.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !get(g:, 'loaded_csv', 0)
+  finish
+endif
+
 let s:column_display = get(g:, 'airline#extensions#csv#column_display', 'Number')
 
 function! airline#extensions#csv#get_column()

autoload/airline/extensions/ctrlp.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !get(g:, 'loaded_ctrlp', 0)
+  finish
+endif
+
 let s:color_template = get(g:, 'airline#extensions#ctrlp#color_template', 'insert')
 
 function! airline#extensions#ctrlp#generate_color_map(dark, light, white)

autoload/airline/extensions/example.vim

@@ -1,6 +1,9 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+" we don't actually want this loaded :P
+finish
+
 " Extension specific variables can be defined the usual fashion.
 if !exists('g:airline#extensions#example#number_of_cats')
   let g:airline#extensions#example#number_of_cats = 42

autoload/airline/extensions/hunks.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !get(g:, 'loaded_signify', 0) && !get(g:, 'loaded_gitgutter', 0)
+  finish
+endif
+
 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', ['+', '~', '-'])
 

autoload/airline/extensions/syntastic.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !exists(':SyntasticCheck')
+  finish
+endif
+
 function! airline#extensions#syntastic#get_warnings()
   let errors = SyntasticStatuslineFlag()
   if strlen(errors) > 0

autoload/airline/extensions/tagbar.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !exists(':TagbarToggle')
+  finish
+endif
+
 let s:flags = get(g:, 'airline#extensions#tagbar#flags', '')
 
 " Arguments: current, sort, fname

autoload/airline/extensions/undotree.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !exists(':UndotreeToggle')
+  finish
+endif
+
 function! airline#extensions#undotree#apply(...)
   if exists('t:undotree')
     if &ft == 'undotree'

autoload/airline/extensions/unite.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !get(g:, 'loaded_unite', 0)
+  finish
+endif
+
 function! airline#extensions#unite#apply(...)
   if &ft == 'unite'
     call a:1.add_section('airline_a', ' Unite ')

autoload/airline/extensions/virtualenv.vim

@@ -1,6 +1,10 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+if !get(g:, 'virtualenv_loaded', 0)
+  finish
+endif
+
 function! airline#extensions#virtualenv#init(ext)
   call a:ext.add_statusline_func('airline#extensions#virtualenv#apply')
 endfunction