reltool doesn't like non-numeric version numbers in directory names

foo_app.app.src

%% -*- erlang -*-
{application, foo_app,
 [
  %% This application has a non-numeric version number.
  {vsn, "abc"}]}.

rebar.config

%% -*- erlang -*-

{sub_dirs, ["foo_app", "bar_rel"]}.

reltool.config

%% -*- erlang -*-
{sys,
 [
  {lib_dirs, ["../apps"]},
  {rel, "bar_rel", "1", [foo_app]},
  {rel, "start_clean", "1", [kernel, stdlib]}]}.

try.sh

#!/bin/sh
mysubdir=$1
if [ -z "$mysubdir" ]; then
    echo "Usage: $0 subdirname"
    echo ""
    echo "subdirname is the directory name that the foo_app application will"
    echo "be symlinked to in the apps/ directory.  My observation is that"
    echo "reltool accepts 'foo_app' and 'foo_app-1', but rejects 'foo_app-abc',"
    echo "while starting an application works for all three names."
    exit 1
fi

echo Compiling foo_app
rebar compile

echo Creating/cleaning apps
rm -rf apps
mkdir apps

echo Symlinking foo_app into apps/$mysubdir
ln -sf $PWD/foo_app apps/$mysubdir

echo Try starting the application
env ERL_LIBS=$PWD/apps erl -noshell -eval 'io:format("application:start(foo_app) -> ~p~n", [application:start(foo_app)])' -s init stop

echo Try building the release
rebar generate