feat: Add option to check buftype option before enabling

Closes #101

Instead of only having a big list of "naughty" filetypes, have an option
to check for the `buftype` and skip if set to anything.

Author: somini

autoload/indent_guides.vim

@@ -284,6 +284,11 @@ endfunction
 " Detect if any of the buffer filetypes should be excluded.
 "
 function! indent_guides#exclude_filetype() abort
+  if exists('g:indent_guides_exclude_buftype')
+    if g:indent_guides_exclude_buftype && &buftype != ''
+      return 1
+    endif
+  endif
   for ft in split(&ft, '\.')
     if index(g:indent_guides_exclude_filetypes, ft) > -1
       return 1

doc/indent_guides.txt

@@ -170,6 +170,14 @@ Default: 0. Values: 0 or 1.
   let g:indent_guides_enable_on_vim_startup = 0
 <
 
+------------------------------------------------------------------------------
+                                             *'indent_guides_exclude_buftype'*
+Use this option to try and disable the plugin on non-file buffers
+
+Default: 0. Values: 0 or 1
+>
+  let g:indent_guides_exclude_buftype = 0
+<
 ------------------------------------------------------------------------------
                                              *'indent_guides_exclude_filetypes'*
 Use this option to specify a list of filetypes to disable the plugin for.