[#149002995] stop eating edoc path config

be a little smarter when generating edocs; loof for some
sort of doc path and then replace w/e was there with the
updated doc paths

src/rebar_prv_edoc.erl

@@ -84,9 +84,8 @@ format_error(Reason) ->
 has_configured_paths(EdocOpts) ->
     proplists:get_value(dir, EdocOpts) =/= undefined.
 
-add_to_paths([], Path) ->
-    [{doc_path, [Path]}];
-add_to_paths([{doc_path, Paths}|T], Path) ->
-    [{doc_path, [Path | Paths]} | T];
-add_to_paths([H|T], Path) ->
-    [H | add_to_paths(Path, T)].
+add_to_paths(Opts, Path) ->
+    case proplists:get_value(doc_path, Opts) of
+        undefined -> [{doc_path, [Path]} | Opts];
+        Paths -> lists:keyreplace(doc_path, 1, Opts, {doc_path, [Path | Paths]})
+    end.