Make it possible to exclude color schemes in $VIMRUNTIME/colors

(suggested by Arun Subramanian in private e-mail)

README.md

@@ -51,6 +51,10 @@ A list with names of color schemes to be ignored by the plug-in. By default the
 
     :let g:colorscheme_switcher_exclude = ['default', 'test']
 
+### The `g:colorscheme_switcher_exclude_builtins` option
+
+If you set this variable to 1 (true) the color schemes bundled with Vim (installed in `$VIMRUNTIME`) are ignored and instead only the color schemes that you specifically installed in your Vim profile are used.
+
 ### The `g:colorscheme_switcher_command` option
 
 This option is a string specifying the Vim command used to switch between color schemes. It defaults to the [:colorscheme] [cs] command. You can set this option to integrate the vim-colorscheme-switcher plug-in with other plug-ins like [colorsupport.vim](https://github.com/vim-scripts/colorsupport.vim) and [guicolorscheme.vim](https://github.com/vim-scripts/guicolorscheme.vim).

autoload/xolox/colorscheme_switcher.vim

@@ -1,9 +1,9 @@
 " Vim plug-in
 " Maintainer: Peter Odding <peter@peterodding.com>
-" Last Change: June 25, 2014
+" Last Change: November 19, 2014
 " URL: http://peterodding.com/code/vim/colorscheme-switcher
 
-let g:xolox#colorscheme_switcher#version = '0.4.1'
+let g:xolox#colorscheme_switcher#version = '0.5'
 
 " Dictionary with previously seen links between highlighting groups.
 if !exists('s:known_links')
@@ -60,15 +60,20 @@ endfunction
 
 function! xolox#colorscheme_switcher#find_names() " {{{1
   " Get a sorted list with the available color schemes.
-  let list = []
+  let matches = {}
+  let exclude_list = xolox#misc#option#get('colorscheme_switcher_exclude', [])
+  let exclude_builtins = xolox#misc#option#get('colorscheme_switcher_exclude_builtins', 0)
   for fname in split(globpath(&runtimepath, 'colors/*.vim'), '\n')
     let name = fnamemodify(fname, ':t:r')
-    let exclude = xolox#misc#option#get('colorscheme_switcher_exclude', [])
-    if index(list, name) == -1 && index(exclude, name) == -1
-      call add(list, name)
+    " Ignore names in the exclude list.
+    if index(exclude_list, name) == -1
+      " Ignore color schemes bundled with Vim?
+      if !(exclude_builtins && xolox#misc#path#starts_with(fname, $VIMRUNTIME))
+        let matches[name] = 1
+      endif
     endif
   endfor
-  return sort(list, 1)
+  return sort(keys(matches), 1)
 endfunction
 
 function! xolox#colorscheme_switcher#find_links() " {{{1

doc/colorscheme-switcher.txt

@@ -13,7 +13,8 @@ Contents ~
   1. The |g:colorscheme_switcher_define_mappings| option
   2. The |g:colorscheme_switcher_keep_background| option
   3. The |g:colorscheme_switcher_exclude| option
-  4. The |g:colorscheme_switcher_command| option
+  4. The |g:colorscheme_switcher_exclude_builtins| option
+  5. The |g:colorscheme_switcher_command| option
  5. See also                                    |colorscheme-switcher-see-also|
  6. Known problems                        |colorscheme-switcher-known-problems|
  7. Contact                                      |colorscheme-switcher-contact|
@@ -112,6 +113,13 @@ list is empty. Here's an example of how you can set this:
 >
   :let g:colorscheme_switcher_exclude = ['default', 'test']
 <
+-------------------------------------------------------------------------------
+The *g:colorscheme_switcher_exclude_builtins* option
+
+If you set this variable to 1 (true) the color schemes bundled with Vim
+(installed in '$VIMRUNTIME') are ignored and instead only the color schemes
+that you specifically installed in your Vim profile are used.
+
 -------------------------------------------------------------------------------
 The *g:colorscheme_switcher_command* option