Add option g:indent_guides_default_mapping

Author: suy

doc/indent_guides.txt

@@ -168,6 +168,14 @@ map it to other keys. For example:
   :nmap <silent> <Leader>ig <Plug>IndentGuidesToggle
 <
 
+The plugin will not provide the default mapping if either:
+  * You already have something mapped to <Plug>IndentGuidesToggle.
+  * You are already using the <Leader>ig key sequence.
+  * You set to 0 the variable g:indent_guides_default_mapping:
+>
+  let g:indent_guides_default_mapping=0
+<
+
 You can also map some other commands that are not mapped by default. For
 example:
 >

plugin/indent_guides.vim

@@ -53,13 +53,15 @@ call s:InitVariable('g:indent_guides_start_level',           1 )
 call s:InitVariable('g:indent_guides_enable_on_vim_startup', 0 )
 call s:InitVariable('g:indent_guides_debug',                 0 )
 call s:InitVariable('g:indent_guides_space_guides',          1 )
+call s:InitVariable('g:indent_guides_default_mapping',       1 )
 
 if !exists('g:indent_guides_exclude_filetypes')
   let g:indent_guides_exclude_filetypes = ['help']
 endif
 
 " Default mapping
 if !hasmapto('<Plug>IndentGuidesToggle', 'n') && maparg('<Leader>ig', 'n') == ''
+    \ && g:indent_guides_default_mapping != 0
   nmap <silent><unique> <Leader>ig <Plug>IndentGuidesToggle
 endif