support reasonable versioning for erlware_commons

You should get the latest and greatest rebar to build this.

Signed-off-by: Jordan Wilberding <diginux@gmail.com>

src/erlware_commons.app.src

@@ -1,7 +1,7 @@
 %% -*- mode: Erlang; fill-column: 75; comment-column: 50; -*-
 {application, erlware_commons,
  [{description, "Additional standard library for Erlang"},
-  {vsn, "0.8.0"},
+  {vsn, git},
   {modules, []},
   {registered, []},
   {applications, [kernel, stdlib]}]}.

src/erlware_commons.app.src.script

@@ -0,0 +1,22 @@
+%% -*- mode: Erlang; erlang-indent-level: 4; indent-tabs-mode: nil; fill-column: 80 -*-
+
+[{application, AppName, Details0}] = CONFIG,
+
+%% Get the tag timestamp and minimal ref from the system. The
+%% timestamp is really important from an ordering perspective.
+{ok, RawRef} = rebar_utils:sh("git log -n 1 --pretty=format:'%ct.%h\n' .", []),
+{ok, RawTag} = rebar_utils:sh("git describe --always --abbrev=0 --tags "
+                              "`git log -n 1 --pretty=format:%h .`", []),
+
+%% Cleanup the tag and the Ref information. Basically leading 'v's and
+%% whitespace needs to go away.
+Tag = re:replace(RawTag, "(^v)|\\s", "", [global]),
+Ref = re:replace(RawRef, "\\s", "", [global]),
+
+%% Create the valid [semver](http://semver.org) version from the tag
+Vsn = erlang:binary_to_list(erlang:iolist_to_binary([Tag, "+build.", Ref])),
+
+%% Replace the old version with the new one
+Details1 = lists:keyreplace(vsn, 1, Details0, {vsn, Vsn}),
+
+[{application, AppName, Details1}].