Suppport a vsn signature with a git implementation

rebar.config

@@ -5,7 +5,7 @@
          {git, "https://github.com/erlware/rebar_vsn_plugin.git",
           {branch, "master"}}}]}.
 
-{erl_first_files, ["ec_dictionary"]}.
+{erl_first_files, ["ec_dictionary", "ec_vsn"]}.
 
 %% Compiler Options ============================================================
 {erl_opts,

src/ec_git_vsn.erl

@@ -0,0 +1,79 @@
+%%% vi:ts=4 sw=4 et
+%%%-------------------------------------------------------------------
+%%% @author Eric Merritt <ericbmerritt@gmail.com>
+%%% @copyright 2011 Erlware, LLC.
+%%% @doc
+%%%  This provides an implementation of the ec_vsn for git. That is
+%%%  it is capable of returning a semver for a git repository
+%%% see ec_vsn
+%%% see ec_semver
+%%% @end
+%%%-------------------------------------------------------------------
+-module(ec_git_vsn).
+
+-behaviour(ec_vsn).
+
+%% API
+-export([new/0,
+         vsn/1]).
+
+-export_type([t/0]).
+
+%%%===================================================================
+%%% Types
+%%%===================================================================
+%% This should be opaque, but that kills dialyzer so for now we export it
+%% however you should not rely on the internal representation here
+-type t() :: {}.
+
+%%%===================================================================
+%%% API
+%%%===================================================================
+
+-spec new() -> t().
+new() ->
+    {}.
+
+-spec vsn(t()) -> {ok, string()} | {error, Reason::any()}.
+vsn(_Data) ->
+    Result = do_cmd("git describe --tags --always"),
+    case re:split(Result, "-") of
+        [Vsn, Count, RefTag] ->
+            erlang:iolist_to_binary([strip_leading_v(Vsn),
+                                     <<"+build.">>,
+                                     Count,
+                                     <<".ref.">>,
+                                     RefTag]);
+        [VsnOrRefTag] ->
+            case re:run(VsnOrRefTag, "^[0-9a-fA-F]+$") of
+                {match, _} ->
+                    find_vsn_from_start_of_branch(VsnOrRefTag);
+                nomatch ->
+                    strip_leading_v(VsnOrRefTag)
+            end;
+        _ ->
+            {error, {invalid_result, Result}}
+    end.
+
+%%%===================================================================
+%%% Internal Functions
+%%%===================================================================
+-spec strip_leading_v(string()) -> string().
+strip_leading_v(Vsn) ->
+    case re:run(Vsn, "v?(.+)", [{capture, [1], binary}]) of
+        {match, [NVsn]} ->
+            NVsn;
+        _ ->
+            Vsn
+    end.
+
+-spec find_vsn_from_start_of_branch(string()) -> string().
+find_vsn_from_start_of_branch(RefTag) ->
+    Count = do_cmd("git rev-list HEAD --count"),
+    erlang:iolist_to_binary("0.0.0+build.", Count, ".ref.", RefTag).
+
+do_cmd(Cmd) ->
+    trim_whitespace(os:cmd(Cmd)).
+
+trim_whitespace(Input) ->
+     re:replace(Input, "\\s+", "", [global]).

src/ec_vsn.erl

@@ -0,0 +1,66 @@
+%%% vi:ts=4 sw=4 et
+%%%-------------------------------------------------------------------
+%%% @author Eric Merritt <ericbmerritt@gmail.com>
+%%% @copyright 2014 Erlware, LLC.
+%%% @doc
+%%%  Provides a signature to manage returning semver formatted versions
+%%%  from various version control repositories.
+%%%
+%%%  This interface is a member of the Erlware Commons Library.
+%%% @end
+%%%-------------------------------------------------------------------
+-module(ec_vsn).
+
+%% API
+-export([new/1,
+         vsn/1]).
+
+-export_type([t/0]).
+
+%%%===================================================================
+%%% Types
+%%%===================================================================
+
+-record(t, {callback, data}).
+
+%% This should be opaque, but that kills dialyzer so for now we export it
+%% however you should not rely on the internal representation here
+-type t() :: #t{}.
+
+-ifdef(have_callback_support).
+
+-callback new() -> any().
+-callback vsn(any()) -> {ok, string()} | {error, Reason::any()}.
+
+-else.
+
+%% In the case where R14 or lower is being used to compile the system
+%% we need to export a behaviour info
+-export([behaviour_info/1]).
+-spec behaviour_info(atom()) -> [{atom(), arity()}] | undefined.
+behaviour_info(callbacks) ->
+    [{new, 0},
+     {vsn, 1}];
+behaviour_info(_Other) ->
+    undefined.
+-endif.
+
+%%%===================================================================
+%%% API
+%%%===================================================================
+
+%% @doc create a new dictionary object from the specified module. The
+%% module should implement the dictionary behaviour.
+%%
+%% @param ModuleName The module name.
+-spec new(module()) -> t().
+new(ModuleName) when erlang:is_atom(ModuleName) ->
+    #t{callback = ModuleName, data = ModuleName:new()}.
+
+%% @doc Return the semver or an error depending on what is possible
+%% with this implementation in this directory.
+%%
+%% @param The dictionary object
+-spec vsn(t()) ->  {ok, string()} | {error, Reason::any()}.
+vsn(#t{callback = Mod, data = Data}) ->
+    Mod:vsn(Data).