Fallback to ag if rg is not present

vim/settings/ctrlp.vim

@@ -8,6 +8,12 @@ if executable('rg')
 
   " rg is fast enough that CtrlP doesn't need to cache
   let g:ctrlp_use_caching = 0
+elseif executable('ag')
+  " Use ag in CtrlP for listing files. Lightning fast and respects .gitignore
+  let g:ctrlp_user_command = 'ag %s --files-with-matches -g "" --ignore "\.git$\|\.hg$\|\.svn$"'
+
+  " ag is fast enough that CtrlP doesn't need to cache
+  let g:ctrlp_use_caching = 0
 else
   " Fall back to using git ls-files if Ag is not available
   let g:ctrlp_custom_ignore = '\.git$\|\.hg$\|\.svn$'