reworking of help display and parse of commands

19 files changed, 165 insertions, 228 deletions

diff --git a/ebin/rebar.app b/ebin/rebar.app
index 2351695..967eb8e 100644
--- a/ebin/rebar.app
+++ b/ebin/rebar.app
@@ -10,11 +10,11 @@
                         rebar_erlydtl_compiler,rebar_fetch,rebar_file_utils,
                         rebar_log,rebar_otp_app,rebar_packages,rebar_provider,
                         rebar_prv_app_discovery,rebar_prv_compile,
-                        rebar_prv_deps,rebar_prv_escripter,
+                        rebar_prv_deps,rebar_prv_escripter,rebar_prv_help,
                         rebar_prv_install_deps,rebar_prv_lock,rebar_prv_new,
                         rebar_prv_packages,rebar_prv_release,rebar_prv_shell,
-                        rebar_prv_tar,rebar_prv_update,rebar_state,
-                        rebar_templater,rebar_topo,rebar_utils,
+                        rebar_prv_tar,rebar_prv_update,rebar_prv_version,
+                        rebar_state,rebar_templater,rebar_topo,rebar_utils,
                         'relx.config_dtl','sup.erl_dtl','sys.config_dtl',
                         'vm.args_dtl']},
               {registered,[]},
@@ -26,4 +26,5 @@
                                 rebar_prv_packages,rebar_erlydtl_compiler,
                                 rebar_prv_compile,rebar_prv_app_discovery,
                                 rebar_prv_shell,rebar_prv_tar,rebar_prv_new,
-                                rebar_prv_update,rebar_prv_release]}]}]}.
+                                rebar_prv_update,rebar_prv_release,
+                                rebar_prv_version,rebar_prv_help]}]}]}.
diff --git a/src/rebar.app.src b/src/rebar.app.src
index 818a0c7..59f35ca 100644
--- a/src/rebar.app.src
+++ b/src/rebar.app.src
@@ -33,6 +33,8 @@
                      rebar_prv_tar,
                      rebar_prv_new,
                      rebar_prv_update,
-                     rebar_prv_release]}
+                     rebar_prv_release,
+                     rebar_prv_version,
+                     rebar_prv_help]}
         ]}
  ]}.
diff --git a/src/rebar3.erl b/src/rebar3.erl
index d0a6baa..f29eaec 100644
--- a/src/rebar3.erl
+++ b/src/rebar3.erl
@@ -28,25 +28,13 @@
 
 -export([main/1,
          run/2,
-         help/0,
+         option_spec_list/0,
          parse_args/1,
          version/0,
          log_level/1]).
 
 -include("rebar.hrl").
 
--ifndef(BUILD_TIME).
--define(BUILD_TIME, "undefined").
--endif.
-
--ifndef(VCS_INFO).
--define(VCS_INFO, "undefined").
--endif.
-
--ifndef(OTP_INFO).
--define(OTP_INFO, "undefined").
--endif.
-
 -define(DEFAULT_JOBS, 3).
 
 %% ====================================================================
@@ -68,52 +56,23 @@ main(Args) ->
     end.
 
 %% Erlang-API entry point
-run(BaseConfig, Commands) ->
+run(BaseState, Command) ->
     _ = application:load(rebar),
-    run_aux(BaseConfig, Commands).
+    BaseState1 = rebar_state:set(BaseState, task, Command),
+    run_aux(BaseState1, []).
 
 %% ====================================================================
 %% Internal functions
 %% ====================================================================
 
-run(["help"|RawCmds]) when RawCmds =/= [] ->
-    ok = load_rebar_app(),
-    Cmds = RawCmds,
-    Args = parse_args(Cmds),
-    BaseConfig = init_config(Args),
-    {BaseConfig1, _} = save_options(BaseConfig, Args),
-    BaseConfig2 = init_config1(BaseConfig1),
-    rebar_core:help(BaseConfig2, [list_to_atom(C) || C <- Cmds]);
-run(["help"]) ->
-    help();
-run(["info"|_]) ->
-    %% Catch calls to 'rebar info' to avoid treating plugins' info/2 functions
-    %% as commands.
-    ?CONSOLE("Command 'info' not understood or not applicable~n", []);
-run(["version"]) ->
-    ok = load_rebar_app(),
-    %% Display vsn and build time info
-    version();
 run(RawArgs) ->
     ok = load_rebar_app(),
     %% Parse out command line arguments -- what's left is a list of commands to
     %% run -- and start running commands
     Args = parse_args(RawArgs),
     BaseConfig = init_config(Args),
-    {BaseConfig1, Cmds} = save_options(BaseConfig, Args),
-
-    case rebar_state:get(BaseConfig1, enable_profiling, false) of
-        true ->
-            io:format("Profiling!\n"),
-            try
-                fprof:apply(fun run_aux/2, [BaseConfig1, Cmds])
-            after
-                ok = fprof:profile(),
-                ok = fprof:analyse([{dest, "fprof.analysis"}])
-            end;
-        false ->
-            run_aux(BaseConfig1, Cmds)
-    end.
+    {BaseConfig1, Args1} = set_options(BaseConfig, Args),
+    run_aux(BaseConfig1, Args1).
 
 load_rebar_app() ->
     %% Pre-load the rebar app so that we get default configuration
@@ -164,7 +123,7 @@ init_config1(BaseConfig) ->
             BaseConfig
     end.
 
-run_aux(BaseConfig, Commands) ->
+run_aux(State, Args) ->
     %% Make sure crypto is running
     case crypto:start() of
         ok -> ok;
@@ -174,34 +133,18 @@ run_aux(BaseConfig, Commands) ->
     application:start(public_key),
     application:start(ssl),
     inets:start(),
-    [Command | Args] = Commands,
-    CommandAtom = list_to_atom(Command),
 
-    BaseConfig1 = init_config1(BaseConfig),
+    State1 = init_config1(State),
 
     %% Process each command, resetting any state between each one
-    BaseConfig2 = rebar_state:set(BaseConfig1, base_dir, filename:absname(rebar_state:dir(BaseConfig1))),
+    State2 = rebar_state:set(State1, base_dir, filename:absname(rebar_state:dir(State1))),
     {ok, Providers} = application:get_env(rebar, providers),
-    BaseConfig3 = rebar_state:create_logic_providers(Providers, BaseConfig2),
-    rebar_core:process_command(rebar_state:command_args(BaseConfig3, Args), CommandAtom),
+    State3 = rebar_state:create_logic_providers(Providers, State2),
+    Task = rebar_state:get(State3, task, "help"),
+    rebar_core:process_command(rebar_state:command_args(State3, Args), ec_cnv:to_atom(Task)),
     ok.
 
 %%
-%% print help/usage string
-%%
-help() ->
-    OptSpecList = option_spec_list(),
-    getopt:usage(OptSpecList, "rebar",
-                 "[var=value,...] <command,...>",
-                 [{"var=value", "rebar global variables (e.g. force=1)"},
-                  {"command", "Command to run (e.g. compile)"}]),
-
-    ?CONSOLE("To see a list of built-in commands, execute rebar -c.~n~n", []),
-    ?CONSOLE(
-       "Type 'rebar help <CMD1> <CMD2>' for help on specific commands."
-       "~n~n", []).
-
-%%
 %% Parse command line arguments using getopt and also filtering out any
 %% key=value pairs. What's left is the list of commands to run
 %%
@@ -213,35 +156,26 @@ parse_args(RawArgs) ->
             Args;
         {error, {Reason, Data}} ->
             ?ERROR("~s ~p~n~n", [Reason, Data]),
-            help(),
             rebar_utils:delayed_halt(1)
     end.
 
-save_options(State, {Options, NonOptArgs}) ->
-    %% Check options and maybe halt execution
-    ok = show_info_maybe_halt(Options, NonOptArgs),
-
+set_options(State, {Options, NonOptArgs}) ->
     GlobalDefines = proplists:get_all_values(defines, Options),
 
     State1 = rebar_state:set(State, defines, GlobalDefines),
 
-    %% Setup profiling flag
-    State2 = rebar_state:set(State1, enable_profiling,
-                               proplists:get_bool(profile, Options)),
-
     %% Set global variables based on getopt options
-    State3 = set_global_flag(State2, Options, force),
-    State4 = case proplists:get_value(jobs, Options, ?DEFAULT_JOBS) of
-                  ?DEFAULT_JOBS ->
-                      State3;
-                  Jobs ->
-                      rebar_state:set(State3, jobs, Jobs)
-              end,
+    State2 = set_global_flag(State1, Options, force),
+    State3 = case proplists:get_value(jobs, Options, ?DEFAULT_JOBS) of
+                 ?DEFAULT_JOBS ->
+                     State2;
+                 Jobs ->
+                     rebar_state:set(State2, jobs, Jobs)
+             end,
+
+    Task = proplists:get_value(task, Options, "help"),
 
-    %% Filter all the flags (i.e. strings of form key=value) from the
-    %% command line arguments. What's left will be the commands to run.
-    {State5, RawCmds} = filter_flags(State4, NonOptArgs, []),
-    {State5, RawCmds}.
+    {rebar_state:set(State3, task, Task), NonOptArgs}.
 
 %%
 %% get log level based on getopt option
@@ -265,8 +199,8 @@ log_level(Options) ->
 %%
 version() ->
     {ok, Vsn} = application:get_key(rebar, vsn),
-    ?CONSOLE("rebar ~s ~s ~s ~s\n",
-             [Vsn, ?OTP_INFO, ?BUILD_TIME, ?VCS_INFO]).
+    ?CONSOLE("rebar ~s on Erlang/OTP ~s Erts ~s~n",
+             [Vsn, erlang:system_info(otp_release), erlang:system_info(version)]).
 
 
 %%
@@ -282,58 +216,6 @@ set_global_flag(State, Options, Flag) ->
     rebar_state:set(State, Flag, Value).
 
 %%
-%% show info and maybe halt execution
-%%
-show_info_maybe_halt(Opts, NonOptArgs) ->
-    false = show_info_maybe_halt(help, Opts, fun help/0),
-    false = show_info_maybe_halt(commands, Opts, fun commands/0),
-    false = show_info_maybe_halt(version, Opts, fun version/0),
-    case NonOptArgs of
-        [] ->
-            ?CONSOLE("No command to run specified!~n",[]),
-            help(),
-            rebar_utils:delayed_halt(1);
-        _ ->
-            ok
-    end.
-
-show_info_maybe_halt(O, Opts, F) ->
-    case proplists:get_bool(O, Opts) of
-        true ->
-            F(),
-            rebar_utils:delayed_halt(0);
-        false ->
-            false
-    end.
-
-%%
-%% print known commands
-%%
-commands() ->
-    S = <<"
-clean                                    Clean
-compile                                  Compile sources
-
-do
-
-escriptize                               Generate escript archive
-
-shell                                    Start a shell similar to
-                                         'erl -pa ebin -pa deps/*/ebin'
-
-update [dep]                             Update source dep
-
-ct
-eunit
-
-new
-
-help                                     Show the program options
-version                                  Show version information
-">>,
-    io:put_chars(S).
-
-%%
 %% options accepted via getopt
 %%
 option_spec_list() ->
@@ -343,55 +225,10 @@ option_spec_list() ->
                  [Jobs]),
     [
      %% {Name, ShortOpt, LongOpt, ArgSpec, HelpMsg}
-     {help,     $h, "help",     undefined, "Show the program options"},
-     {commands, $c, "commands", undefined, "Show available commands"},
-     {verbose,  $v, "verbose",  integer,   "Verbosity level (-v, -vv)"},
-     {quiet,    $q, "quiet",    boolean,   "Quiet, only print error messages"},
-     {version,  $V, "version",  undefined, "Show version information"},
-     {force,    $f, "force",    undefined, "Force"},
-     {defines,  $D, undefined,  string,    "Define compiler macro"},
+     {help,     $h, "help",     undefined, "Print this help."},
+     {verbose,  $v, "verbose",  integer,   "Verbosity level (-v, -vv)."},
+     {version,  $V, "version",  undefined, "Show version information."},
      {jobs,     $j, "jobs",     integer,   JobsHelp},
-     {config,   $C, "config",   string,    "Rebar config file to use"},
-     {profile,  $p, "profile",  undefined, "Profile this run of rebar"},
-     {keep_going, $k, "keep-going", undefined,
-      "Keep running after a command fails"},
-     {recursive, $r, "recursive", boolean,
-      "Apply commands to subdirs and dependencies"}
-    ].
-
-%%
-%% Seperate all commands (single-words) from flags (key=value) and store
-%% values into the rebar_state global storage.
-%%
-filter_flags(State, [], Commands) ->
-    {State, lists:reverse(Commands)};
-filter_flags(State, [Item | Rest], Commands) ->
-    case string:tokens(Item, "=") of
-        [Command] ->
-            filter_flags(State, Rest, [Command | Commands]);
-        [KeyStr, RawValue] ->
-            Key = list_to_atom(KeyStr),
-            Value = case Key of
-                        verbose ->
-                            list_to_integer(RawValue);
-                        _ ->
-                            RawValue
-                    end,
-            State1 = rebar_state:set(State, Key, Value),
-            filter_flags(State1, Rest, Commands);
-        Other ->
-            ?CONSOLE("Ignoring command line argument: ~p\n", [Other]),
-            filter_flags(State, Rest, Commands)
-    end.
-
-command_names() ->
-    [
-     "clean",
-     "compile",
-     "release",
-     "update",
-     "escriptize",
-     "help",
-     "shell",
-     "version"
+     {config,   $C, "config",   string,    "Rebar config file to use."},
+     {task,     undefined, undefined, string, "Task to run."}
     ].
diff --git a/src/rebar_erlydtl_compiler.erl b/src/rebar_erlydtl_compiler.erl
index b90ef37..88ee20f 100644
--- a/src/rebar_erlydtl_compiler.erl
+++ b/src/rebar_erlydtl_compiler.erl
@@ -104,7 +104,7 @@
 
 -include("rebar.hrl").
 
--define(PROVIDER, compile).
+-define(PROVIDER, erlydtl).
 -define(DEPS, []).
 
 %% ===================================================================
@@ -114,13 +114,13 @@
 -spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
 init(State) ->
     State1 = rebar_state:add_provider(State, #provider{name = ?PROVIDER,
-                                                        provider_impl = ?MODULE,
-                                                        bare = false,
-                                                        deps = ?DEPS,
-                                                        example = "compile",
-                                                        short_desc = "",
-                                                        desc = "",
-                                                        opts = []}),
+                                                       provider_impl = ?MODULE,
+                                                       bare = false,
+                                                       deps = ?DEPS,
+                                                       example = "rebar erlydtl compile",
+                                                       short_desc = "Compile erlydtl templates.",
+                                                       desc = "",
+                                                       opts = []}),
     {ok, State1}.
 
 do(Config) ->
diff --git a/src/rebar_provider.erl b/src/rebar_provider.erl
index 30f7d80..3c80a80 100644
--- a/src/rebar_provider.erl
+++ b/src/rebar_provider.erl
@@ -6,6 +6,7 @@
          impl/1,
          get_provider/2,
          get_target_providers/2,
+         help/1,
          format/1]).
 
 -export_type([t/0]).
@@ -73,13 +74,26 @@ do(Provider, State) ->
 impl(Provider) ->
     Provider#provider.name.
 
+help(State) ->
+    Providers = rebar_state:providers(State),
+    Help = lists:sort([{ec_cnv:to_list(P#provider.name), P#provider.short_desc} || P <- Providers,
+                                                                                   P#provider.bare =/= true]),
+    Longest = lists:max([length(X) || {X, _} <- Help]),
+
+    lists:foreach(fun({Name, ShortDesc}) ->
+                          Length = length(Name),
+                          Spacing = lists:duplicate(Longest - Length + 8, " "),
+                          io:format("~s~s~s~n", [Name, Spacing, ShortDesc])
+                  end, Help).
+
+
 %% @doc print the provider module name
 %%
 %% @param T - The provider
 %% @return An iolist describing the provider
 -spec format(t()) -> iolist().
-format(#provider{provider_impl=Mod}) ->
-    erlang:atom_to_list(Mod).
+format(#provider{name=Name}) ->
+    atom_to_list(Name).
 
 get_target_providers(Target, State) ->
     Providers = rebar_state:providers(State),
diff --git a/src/rebar_prv_app_discovery.erl b/src/rebar_prv_app_discovery.erl
index c1f5708..897a38d 100644
--- a/src/rebar_prv_app_discovery.erl
+++ b/src/rebar_prv_app_discovery.erl
@@ -21,7 +21,7 @@
 init(State) ->
     State1 = rebar_state:add_provider(State, #provider{name = ?PROVIDER,
                                                        provider_impl = ?MODULE,
-                                                       bare = false,
+                                                       bare = true,
                                                        deps = ?DEPS,
                                                        example = "",
                                                        short_desc = "",
diff --git a/src/rebar_prv_compile.erl b/src/rebar_prv_compile.erl
index 5e7bd82..d89a4b0 100644
--- a/src/rebar_prv_compile.erl
+++ b/src/rebar_prv_compile.erl
@@ -22,7 +22,7 @@ init(State) ->
                                                         bare = false,
                                                         deps = ?DEPS,
                                                         example = "rebar compile",
-                                                        short_desc = "",
+                                                        short_desc = "Compile apps .app.src and .erl files.",
                                                         desc = "",
                                                         opts = []}),
     {ok, State1}.
diff --git a/src/rebar_prv_deps.erl b/src/rebar_prv_deps.erl
index 834e7dc..111f32f 100644
--- a/src/rebar_prv_deps.erl
+++ b/src/rebar_prv_deps.erl
@@ -14,7 +14,7 @@
 init(State) ->
     State1 = rebar_state:add_provider(State, #provider{name = ?PROVIDER,
                                                        provider_impl = ?MODULE,
-                                                       bare = false,
+                                                       bare = true,
                                                        deps = ?DEPS,
                                                        example = "rebar deps",
                                                        short_desc = "List dependencies",
diff --git a/src/rebar_prv_escripter.erl b/src/rebar_prv_escripter.erl
index f153564..418ac6c 100644
--- a/src/rebar_prv_escripter.erl
+++ b/src/rebar_prv_escripter.erl
@@ -53,8 +53,8 @@ init(State) ->
                                                         provider_impl = ?MODULE,
                                                         bare = false,
                                                         deps = ?DEPS,
-                                                        example = "escriptize",
-                                                        short_desc = "",
+                                                        example = "rebar escriptize",
+                                                        short_desc = "Build escript from project.",
                                                         desc = "",
                                                         opts = []}),
     {ok, State1}.
diff --git a/src/rebar_prv_help.erl b/src/rebar_prv_help.erl
new file mode 100644
index 0000000..a9949e7
--- /dev/null
+++ b/src/rebar_prv_help.erl
@@ -0,0 +1,48 @@
+%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
+%% ex: ts=4 sw=4 et
+
+-module(rebar_prv_help).
+
+-behaviour(rebar_provider).
+
+-export([init/1,
+         do/1]).
+
+-include("rebar.hrl").
+
+-define(PROVIDER, help).
+-define(DEPS, []).
+
+%% ===================================================================
+%% Public API
+%% ===================================================================
+
+-spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
+init(State) ->
+    State1 = rebar_state:add_provider(State, #provider{name = ?PROVIDER,
+                                                       provider_impl = ?MODULE,
+                                                       bare = false,
+                                                       deps = ?DEPS,
+                                                       example = "rebar help <task>",
+                                                       short_desc = "Display a list of tasks or help for a given task or subtask.",
+                                                       desc = "",
+                                                       opts = []}),
+    {ok, State1}.
+
+-spec do(rebar_state:t()) -> {ok, rebar_state:t()} | relx:error().
+do(State) ->
+    help(State),
+    {ok, State}.
+
+%%
+%% print help/usage string
+%%
+help(State) ->
+    ?CONSOLE("Rebar is a tool for working with Erlang projects.~n~n", []),
+    OptSpecList = rebar3:option_spec_list(),
+    getopt:usage(OptSpecList, "rebar", "", []),
+    ?CONSOLE("~nSeveral tasks are available:~n", []),
+
+    rebar_provider:help(State),
+
+    ?CONSOLE("~nRun 'rebar help <TASK>' for details.~n~n", []).
diff --git a/src/rebar_prv_install_deps.erl b/src/rebar_prv_install_deps.erl
index 87db8b0..d20f2b5 100644
--- a/src/rebar_prv_install_deps.erl
+++ b/src/rebar_prv_install_deps.erl
@@ -55,7 +55,7 @@
 init(State) ->
     State1 = rebar_state:add_provider(State, #provider{name = ?PROVIDER,
                                                        provider_impl = ?MODULE,
-                                                       bare = false,
+                                                       bare = true,
                                                        deps = ?DEPS,
                                                        example = undefined,
                                                        short_desc = "Install dependencies",
diff --git a/src/rebar_prv_lock.erl b/src/rebar_prv_lock.erl
index db6e753..b4a7d8d 100644
--- a/src/rebar_prv_lock.erl
+++ b/src/rebar_prv_lock.erl
@@ -18,10 +18,10 @@
 init(State) ->
     State1 = rebar_state:add_provider(State, #provider{name = ?PROVIDER,
                                                        provider_impl = ?MODULE,
-                                                       bare = false,
+                                                       bare = true,
                                                        deps = ?DEPS,
                                                        example = "",
-                                                       short_desc = "Locks dependencies",
+                                                       short_desc = "Locks dependencies.",
                                                        desc = info("Locks dependencies"),
                                                        opts = []}),
     {ok, State1}.
diff --git a/src/rebar_prv_new.erl b/src/rebar_prv_new.erl
index 528c95e..ed3c1b4 100644
--- a/src/rebar_prv_new.erl
+++ b/src/rebar_prv_new.erl
@@ -21,7 +21,7 @@ init(State) ->
                                                        bare = false,
                                                        deps = ?DEPS,
                                                        example = "rebar new <template>",
-                                                       short_desc = "",
+                                                       short_desc = "Create new project from templates.",
                                                        desc = info(create),
                                                        opts = []}),
     {ok, State1}.
diff --git a/src/rebar_prv_packages.erl b/src/rebar_prv_packages.erl
index 8b4a963..79c1cd2 100644
--- a/src/rebar_prv_packages.erl
+++ b/src/rebar_prv_packages.erl
@@ -17,7 +17,7 @@ init(State) ->
                                                        bare = false,
                                                        deps = ?DEPS,
                                                        example = "rebar pkgs",
-                                                       short_desc = "List available packages",
+                                                       short_desc = "List available packages.",
                                                        desc = info("List available packages"),
                                                        opts = []}),
     {ok, State1}.
diff --git a/src/rebar_prv_release.erl b/src/rebar_prv_release.erl
index 43a30ca..4203c3a 100644
--- a/src/rebar_prv_release.erl
+++ b/src/rebar_prv_release.erl
@@ -20,13 +20,13 @@
 -spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
 init(State) ->
     State1 = rebar_state:add_provider(State, #provider{name = ?PROVIDER,
-                                                        provider_impl = ?MODULE,
-                                                        bare = false,
-                                                        deps = ?DEPS,
-                                                        example = "rebar release",
-                                                        short_desc = "",
-                                                        desc = "",
-                                                        opts = []}),
+                                                       provider_impl = ?MODULE,
+                                                       bare = false,
+                                                       deps = ?DEPS,
+                                                       example = "rebar release",
+                                                       short_desc = "Build release of project.",
+                                                       desc = "",
+                                                       opts = []}),
     {ok, State1}.
 
 -spec do(rebar_state:t()) -> {ok, rebar_state:t()} | relx:error().
diff --git a/src/rebar_prv_shell.erl b/src/rebar_prv_shell.erl
index ef53518..06195ec 100644
--- a/src/rebar_prv_shell.erl
+++ b/src/rebar_prv_shell.erl
@@ -49,7 +49,7 @@ init(State) ->
                                                         bare = false,
                                                         deps = ?DEPS,
                                                         example = "rebar shell",
-                                                        short_desc = "",
+                                                        short_desc = "Run shell with project apps and deps in path.",
                                                         desc = "",
                                                         opts = []}),
     {ok, State1}.
diff --git a/src/rebar_prv_tar.erl b/src/rebar_prv_tar.erl
index 44d83db..607d533 100644
--- a/src/rebar_prv_tar.erl
+++ b/src/rebar_prv_tar.erl
@@ -24,7 +24,7 @@ init(State) ->
                                                         bare = false,
                                                         deps = ?DEPS,
                                                         example = "rebar tar",
-                                                        short_desc = "",
+                                                        short_desc = "Tar archive of release built of project.",
                                                         desc = "",
                                                         opts = []}),
     {ok, State1}.
diff --git a/src/rebar_prv_update.erl b/src/rebar_prv_update.erl
index 527c582..9df8e60 100644
--- a/src/rebar_prv_update.erl
+++ b/src/rebar_prv_update.erl
@@ -24,7 +24,7 @@ init(State) ->
                                                        bare = false,
                                                        deps = ?DEPS,
                                                        example = "rebar update cowboy",
-                                                       short_desc = "",
+                                                       short_desc = "Update package index or individual dependency.",
                                                        desc = "",
                                                        opts = []}),
     {ok, State1}.
diff --git a/src/rebar_prv_version.erl b/src/rebar_prv_version.erl
new file mode 100644
index 0000000..ab56802
--- /dev/null
+++ b/src/rebar_prv_version.erl
@@ -0,0 +1,35 @@
+%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
+%% ex: ts=4 sw=4 et
+
+-module(rebar_prv_version).
+
+-behaviour(rebar_provider).
+
+-export([init/1,
+         do/1]).
+
+-include("rebar.hrl").
+
+-define(PROVIDER, version).
+-define(DEPS, []).
+
+%% ===================================================================
+%% Public API
+%% ===================================================================
+
+-spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
+init(State) ->
+    State1 = rebar_state:add_provider(State, #provider{name = ?PROVIDER,
+                                                       provider_impl = ?MODULE,
+                                                       bare = false,
+                                                       deps = ?DEPS,
+                                                       example = "rebar version",
+                                                       short_desc = "Print version for rebar and current Erlang.",
+                                                       desc = "",
+                                                       opts = []}),
+    {ok, State1}.
+
+-spec do(rebar_state:t()) -> {ok, rebar_state:t()} | relx:error().
+do(State) ->
+    rebar3:version(),
+    {ok, State}.