Made grep version command's grep POSIX

test/ec_git_vsn_tests.erl

@@ -0,0 +1,15 @@
+-module(ec_git_vsn_tests).
+-include_lib("eunit/include/eunit.hrl").
+-compile([export_all]).
+
+
+%% Hi! This test only works because you've cloned this repo out of git
+%% AND we're tagging this repo with a "v" prefix. Hey, it's better
+%% than nothing.
+vsn_grep_test() ->
+    {ok, VSN} = ec_git_vsn:vsn({"v"}),
+
+    [$v|OtherVSN] = os:cmd("git tag | xargs -I@ git log --format=format:\"%ai @%n\" -1 @ | sort -r | awk '{print $4}' | head -n 1"),
+
+    ?assertEqual(OtherVSN, VSN ++ "\n"),
+    ok.