Implement 'rebar help CMD1 CMD2' and extend common 'rebar help' msg

* allow plugins to print help message for implemented commands
* append core rebar.config options to common 'rebar help' message

25 files changed, 567 insertions, 30 deletions

diff --git a/src/rebar.erl b/src/rebar.erl
index c872ade..ded5ebe 100644
--- a/src/rebar.erl
+++ b/src/rebar.erl
@@ -76,8 +76,18 @@ run(BaseConfig, Commands) ->
 %% Internal functions
 %% ====================================================================
 
+run(["help"|RawCmds]) when RawCmds =/= [] ->
+    ok = load_rebar_app(),
+    Cmds = unabbreviate_command_names(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"|_]) ->
+    help();
 run(["version"]) ->
     ok = load_rebar_app(),
     %% Display vsn and build time info
@@ -138,6 +148,16 @@ init_config({Options, _NonOptArgs}) ->
     %% Initialize vsn cache
     rebar_config:set_xconf(BaseConfig1, vsn_cache, dict:new()).
 
+init_config1(BaseConfig) ->
+    %% Determine the location of the rebar executable; important for pulling
+    %% resources out of the escript
+    ScriptName = filename:absname(escript:script_name()),
+    BaseConfig1 = rebar_config:set_xconf(BaseConfig, escript, ScriptName),
+    ?DEBUG("Rebar location: ~p\n", [ScriptName]),
+    %% Note the top-level directory for reference
+    AbsCwd = filename:absname(rebar_utils:get_cwd()),
+    rebar_config:set_xconf(BaseConfig1, base_dir, AbsCwd).
+
 run_aux(BaseConfig, Commands) ->
     %% Make sure crypto is running
     case crypto:start() of
@@ -148,18 +168,10 @@ run_aux(BaseConfig, Commands) ->
     %% Convert command strings to atoms
     CommandAtoms = [list_to_atom(C) || C <- Commands],
 
-    %% Determine the location of the rebar executable; important for pulling
-    %% resources out of the escript
-    ScriptName = filename:absname(escript:script_name()),
-    BaseConfig1 = rebar_config:set_xconf(BaseConfig, escript, ScriptName),
-    ?DEBUG("Rebar location: ~p\n", [ScriptName]),
-
-    %% Note the top-level directory for reference
-    AbsCwd = filename:absname(rebar_utils:get_cwd()),
-    BaseConfig2 = rebar_config:set_xconf(BaseConfig1, base_dir, AbsCwd),
+    BaseConfig1 = init_config1(BaseConfig),
 
     %% Process each command, resetting any state between each one
-    rebar_core:process_commands(CommandAtoms, BaseConfig2).
+    rebar_core:process_commands(CommandAtoms, BaseConfig1).
 
 %%
 %% print help/usage string
@@ -169,7 +181,29 @@ help() ->
     getopt:usage(OptSpecList, "rebar",
                  "[var=value,...] <command,...>",
                  [{"var=value", "rebar global variables (e.g. force=1)"},
-                  {"command", "Command to run (e.g. compile)"}]).
+                  {"command", "Command to run (e.g. compile)"}]),
+    ?CONSOLE(
+       "Core rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n",
+       [
+        {lib_dirs, []},
+        {sub_dirs, ["dir1", "dir2"]},
+        {plugins, [plugin1, plugin2]},
+        {plugin_dir, "some_other_directory"},
+        {pre_hooks, [{clean, "./prepare_package_files.sh"},
+                     {"linux", compile, "c_src/build_linux.sh"},
+                     {compile, "escript generate_headers"},
+                     {compile, "escript check_headers"}]},
+        {post_hooks, [{clean, "touch file1.out"},
+                      {"freebsd", compile, "c_src/freebsd_tweaks.sh"},
+                      {eunit, "touch file2.out"},
+                      {compile, "touch postcompile.out"}]}
+       ]).
 
 %%
 %% Parse command line arguments using getopt and also filtering out any
diff --git a/src/rebar_abnfc_compiler.erl b/src/rebar_abnfc_compiler.erl
index 0e6749a..37731b5 100644
--- a/src/rebar_abnfc_compiler.erl
+++ b/src/rebar_abnfc_compiler.erl
@@ -47,6 +47,9 @@
 
 -export([compile/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -62,11 +65,23 @@ compile(Config, _AppFile) ->
                             option(module_ext, DtlOpts) ++ ".erl",
                             fun compile_abnfc/3).
 
-
 %% ===================================================================
 %% Internal functions
 %% ===================================================================
 
+info(help, compile) ->
+    ?CONSOLE(
+       "Build ABNF (*.abnf) sources.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n",
+       [
+        {abnfc_opts, [{doc_root, "src"},
+                      {out_dir, "src"},
+                      {source_ext, ".abnfc"},
+                      {module_ext, ""}]}
+       ]).
+
 abnfc_opts(Config) ->
     rebar_config:get(Config, abnfc_opts, []).
 
diff --git a/src/rebar_appups.erl b/src/rebar_appups.erl
index 0aeccb6..722f161 100644
--- a/src/rebar_appups.erl
+++ b/src/rebar_appups.erl
@@ -31,6 +31,9 @@
 
 -export(['generate-appups'/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -define(APPUPFILEFORMAT, "%% appup generated for ~p by rebar (~p)~n"
         "{~p, [{~p, ~p}], [{~p, []}]}.~n").
 
@@ -82,6 +85,13 @@
 %% Internal functions
 %% ===================================================================
 
+info(help, 'generate-appups') ->
+    ?CONSOLE("Generate appup files.~n"
+             "~n"
+             "Valid command line options:~n"
+             "  previous_release=path~n",
+             []).
+
 get_apps(Name, OldVerPath, NewVerPath) ->
     OldApps = rebar_rel_utils:get_rel_apps(Name, OldVerPath),
     ?DEBUG("Old Version Apps: ~p~n", [OldApps]),
diff --git a/src/rebar_asn1_compiler.erl b/src/rebar_asn1_compiler.erl
index d93a2e8..25e3fd3 100644
--- a/src/rebar_asn1_compiler.erl
+++ b/src/rebar_asn1_compiler.erl
@@ -30,6 +30,9 @@
 -export([compile/2,
          clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -48,6 +51,23 @@ clean(_Config, _AppFile) ->
     ok = rebar_file_utils:delete_each(GeneratedFiles),
     ok.
 
+%% ===================================================================
+%% Internal functions
+%% ===================================================================
+
+info(help, compile) ->
+    info_help("Build ASN.1 (*.asn1) sources");
+info(help, clean) ->
+    info_help("Delete ASN.1 (*.asn1) results").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  {asn1_opts, []} (see asn1ct:compile/2 documentation)~n",
+       [Description]).
+
 -spec compile_asn1(file:filename(), file:filename(),
                    rebar_config:config()) -> ok.
 compile_asn1(Source, Target, Config) ->
diff --git a/src/rebar_cleaner.erl b/src/rebar_cleaner.erl
index 9ddeb8a..7a762f5 100644
--- a/src/rebar_cleaner.erl
+++ b/src/rebar_cleaner.erl
@@ -28,6 +28,9 @@
 
 -export([clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -37,3 +40,17 @@ clean(Config, _AppFile) ->
     %% Get a list of files to delete from config and remove them
     FilesToClean = rebar_config:get(Config, clean_files, []),
     lists:foreach(fun (F) -> rebar_file_utils:rm_rf(F) end, FilesToClean).
+
+%% ===================================================================
+%% Internal functions
+%% ===================================================================
+
+info(help, clean) ->
+    ?CONSOLE(
+       "Delete list of files.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n",
+       [
+        {clean_files, ["file", "file2"]}
+       ]).
diff --git a/src/rebar_core.erl b/src/rebar_core.erl
index 5396dd5..e6af2c5 100644
--- a/src/rebar_core.erl
+++ b/src/rebar_core.erl
@@ -26,7 +26,7 @@
 %% -------------------------------------------------------------------
 -module(rebar_core).
 
--export([process_commands/2]).
+-export([process_commands/2, help/2]).
 
 -include("rebar.hrl").
 
@@ -34,6 +34,35 @@
 %% Internal functions
 %% ===================================================================
 
+help(ParentConfig, Commands) ->
+    %% get all core modules
+    {ok, AnyDirModules} = application:get_env(rebar, any_dir_modules),
+    {ok, RawCoreModules} = application:get_env(rebar, modules),
+    AppDirModules = proplists:get_value(app_dir, RawCoreModules),
+    RelDirModules = proplists:get_value(rel_dir, RawCoreModules),
+    CoreModules = AnyDirModules ++ AppDirModules ++ RelDirModules,
+
+    %% get plugin modules
+    Predirs = [],
+    Dir = rebar_utils:get_cwd(),
+    SubdirAssoc = remember_cwd_subdir(Dir, Predirs),
+    Config = maybe_load_local_config(Dir, ParentConfig),
+    {ok, PluginModules} = plugin_modules(Config, SubdirAssoc),
+
+    AllModules = CoreModules ++ PluginModules,
+
+    lists:foreach(
+      fun(Cmd) ->
+              ?CONSOLE("==> help ~p~n~n", [Cmd]),
+              CmdModules = select_modules(AllModules, Cmd, []),
+              Modules = select_modules(CmdModules, info, []),
+              lists:foreach(fun(M) ->
+                                    ?CONSOLE("=== ~p:~p ===~n", [M, Cmd]),
+                                    M:info(help, Cmd),
+                                    ?CONSOLE("~n", [])
+                            end, Modules)
+      end, Commands).
+
 process_commands([], ParentConfig) ->
     AbortTrapped = rebar_config:get_xconf(ParentConfig, abort_trapped, false),
     case {get_operations(ParentConfig), AbortTrapped} of
diff --git a/src/rebar_ct.erl b/src/rebar_ct.erl
index 749d025..d5b1d26 100644
--- a/src/rebar_ct.erl
+++ b/src/rebar_ct.erl
@@ -39,6 +39,9 @@
 
 -export([ct/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -53,6 +56,26 @@ ct(Config, File) ->
 %% ===================================================================
 %% Internal functions
 %% ===================================================================
+
+info(help, ct) ->
+    ?CONSOLE(
+       "Run common_test suites.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "Valid command line options:~n"
+       "  suites=foo,bar - run <test>/foo_SUITE and <test>/bar_SUITE~n"
+       "  case=\"mycase\" - run individual test case foo_SUITE:mycase~n",
+       [
+        {ct_dir, "itest"},
+        {ct_log_dir, "test/logs"},
+        {ct_extra_params, "-boot start_sasl -s myapp"},
+        {ct_use_short_names, true}
+       ]).
+
 run_test_if_present(TestDir, LogDir, Config, File) ->
     case filelib:is_dir(TestDir) of
         false ->
diff --git a/src/rebar_deps.erl b/src/rebar_deps.erl
index 074e929..17d196f 100644
--- a/src/rebar_deps.erl
+++ b/src/rebar_deps.erl
@@ -38,6 +38,8 @@
          'delete-deps'/2,
          'list-deps'/2]).
 
+%% for internal use only
+-export([info/2]).
 
 -record(dep, { dir,
                app,
@@ -203,6 +205,40 @@ do_check_deps(Config) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, compile) ->
+    info_help("Display to be fetched dependencies");
+info(help, 'check-deps') ->
+    info_help("Display to be fetched dependencies");
+info(help, 'get-deps') ->
+    info_help("Fetch dependencies");
+info(help, 'update-deps') ->
+    info_help("Update fetched dependencies");
+info(help, 'delete-deps') ->
+    info_help("Delete fetched dependencies");
+info(help, 'list-deps') ->
+    info_help("List dependencies").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "Valid command line options:~n"
+       "  deps_dir=\"deps\" (override default or rebar.config deps_dir)~n",
+       [
+        Description,
+        {deps_dir, "deps"},
+        {deps, [application_name,
+                {application_name, "1.0.*"},
+                {application_name, "1.0.*",
+                 {git, "git://github.com/basho/rebar.git", {branch, "master"}}},
+                {application_name, "",
+                 {git, "git://github.com/basho/rebar.git", {branch, "master"}},
+                 [raw]}]}
+       ]).
+
 %% Added because of trans deps,
 %% need all deps in same dir and should be the one set by the root rebar.config
 %% Sets a default if root config has no deps_dir set
diff --git a/src/rebar_dia_compiler.erl b/src/rebar_dia_compiler.erl
index 51c075b..f81c734 100644
--- a/src/rebar_dia_compiler.erl
+++ b/src/rebar_dia_compiler.erl
@@ -28,6 +28,9 @@
 
 -export([compile/2, clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -46,6 +49,23 @@ clean(_Config, _AppFile) ->
     ok = rebar_file_utils:delete_each(GeneratedFiles),
     ok.
 
+%% ===================================================================
+%% Internal functions
+%% ===================================================================
+
+info(help, compile) ->
+    info_help("Build Diameter (*.dia) sources");
+info(help, clean) ->
+    info_help("Delete generated Diameter files").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  {dia_opts, []} (see diameter_codegen:from_dict/4 documentation)~n",
+       [Description]).
+
 -spec compile_dia(file:filename(), file:filename(),
                    rebar_config:config()) -> ok.
 compile_dia(Source, Target, Config) ->
diff --git a/src/rebar_edoc.erl b/src/rebar_edoc.erl
index cf0239c..c828d27 100644
--- a/src/rebar_edoc.erl
+++ b/src/rebar_edoc.erl
@@ -39,6 +39,9 @@
 
 -export([doc/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -71,6 +74,14 @@ doc(Config, File) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, doc) ->
+    ?CONSOLE(
+       "Generate Erlang program documentation.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  {edoc_opts, []} (see edoc:application/3 documentation)~n",
+       []).
+
 setup_code_path() ->
     %% Setup code path prior to calling edoc so that edown, asciiedoc,
     %% and the like can work properly when generating their own
diff --git a/src/rebar_erlc_compiler.erl b/src/rebar_erlc_compiler.erl
index 91f8354..caef0d2 100644
--- a/src/rebar_erlc_compiler.erl
+++ b/src/rebar_erlc_compiler.erl
@@ -29,8 +29,9 @@
 -export([compile/2,
          clean/2]).
 
-%% for internal use by only eunit and qc
--export([test_compile/3]).
+%% for internal use only
+-export([test_compile/3,
+         info/2]).
 
 -include("rebar.hrl").
 
@@ -116,8 +117,6 @@ clean(_Config, _AppFile) ->
 
 test_compile(Config, Cmd, OutDir) ->
     %% Obtain all the test modules for inclusion in the compile stage.
-    %% Notice: this could also be achieved with the following
-    %% rebar.config option: {test_compile_opts, [{src_dirs, ["src", "test"]}]}
     TestErls = rebar_utils:find_files("test", ".*\\.erl\$"),
 
     %% Copy source files to eunit dir for cover in case they are not directly
@@ -165,6 +164,42 @@ test_compile(Config, Cmd, OutDir) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, compile) ->
+    info_help("Build *.erl, *.yrl, *.xrl, and *.mib sources");
+info(help, clean) ->
+    info_help("Delete *.erl, *.yrl, *.xrl, and *.mib build results").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n",
+       [
+        Description,
+        {erl_opts, [no_debug_info,
+                    {i, "myinclude"},
+                    {src_dirs, ["src", "src2", "src3"]},
+                    {platform_define,
+                     "(linux|solaris|freebsd|darwin)", 'HAVE_SENDFILE'},
+                    {platform_define, "(linux|freebsd)", 'BACKLOG', 128},
+                    {platform_define, "R13", 'old_inets'}]},
+        {erl_first_files, ["mymib1", "mymib2"]},
+        {mib_opts, []},
+        {mib_first_files, []},
+        {xrl_opts, []},
+        {xrl_first_files, []},
+        {yrl_opts, []},
+        {yrl_first_files, []}
+       ]).
+
 test_compile_config(Config, Cmd) ->
     {Config1, TriqOpts} = triq_opts(Config),
     {Config2, PropErOpts} = proper_opts(Config1),
diff --git a/src/rebar_erlydtl_compiler.erl b/src/rebar_erlydtl_compiler.erl
index aef41c5..4449be6 100644
--- a/src/rebar_erlydtl_compiler.erl
+++ b/src/rebar_erlydtl_compiler.erl
@@ -96,6 +96,9 @@
 
 -export([compile/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -123,11 +126,24 @@ compile(Config, _AppFile) ->
     true = code:set_path(OrigPath),
     Result.
 
-
 %% ===================================================================
 %% Internal functions
 %% ===================================================================
 
+info(help, compile) ->
+    ?CONSOLE(
+       "Build ErlyDtl (*.dtl) sources.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n",
+       [
+        {erlydtl_opts, [{doc_root,   "templates"},
+                        {out_dir,    "ebin"},
+                        {source_ext, ".dtl"},
+                        {module_ext, "_dtl"},
+                        {recursive, true}]}
+       ]).
+
 erlydtl_opts(Config) ->
     Opts = rebar_config:get(Config, erlydtl_opts, []),
     Tuples = [{K,V} || {K,V} <- Opts],
@@ -135,11 +151,14 @@ erlydtl_opts(Config) ->
         [] ->
             [lists:keysort(1, Tuples)];
         Lists ->
-            lists:map(fun(L) ->
-                lists:keysort(1, lists:foldl(fun({K,T}, Acc) ->
-                    lists:keystore(K, 1, Acc, {K, T})
-                end, Tuples, L))
-            end, Lists)
+            lists:map(
+              fun(L) ->
+                      lists:keysort(1,
+                                    lists:foldl(
+                                      fun({K,T}, Acc) ->
+                                              lists:keystore(K, 1, Acc, {K, T})
+                                      end, Tuples, L))
+              end, Lists)
     end.
 
 option(Opt, DtlOpts) ->
diff --git a/src/rebar_escripter.erl b/src/rebar_escripter.erl
index 706cf7c..0cc43ef 100644
--- a/src/rebar_escripter.erl
+++ b/src/rebar_escripter.erl
@@ -29,6 +29,9 @@
 -export([escriptize/2,
          clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 -include_lib("kernel/include/file.hrl").
 
@@ -108,6 +111,30 @@ clean(Config0, AppFile) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, escriptize) ->
+    info_help("Generate escript archive");
+info(help, clean) ->
+    info_help("Delete generated escript archive").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n",
+       [
+        Description,
+        {escript_name, "application"},
+        {escript_incl_apps, []},
+        {escript_shebang, "#!/usr/bin/env escript\n"},
+        {escript_comment, "%%\n"},
+        {escript_emu_args, "%%! -pa application/application/ebin\n"}
+       ]).
+
 get_app_beams([], Acc) ->
     Acc;
 get_app_beams([App | Rest], Acc) ->
diff --git a/src/rebar_eunit.erl b/src/rebar_eunit.erl
index a7f4aca..cdc0787 100644
--- a/src/rebar_eunit.erl
+++ b/src/rebar_eunit.erl
@@ -61,7 +61,7 @@
 %% Additionally, for projects that have separate folders for the core
 %% implementation, and for the unit tests, then the following
 %% <code>rebar.config</code> option can be provided:
-%% <code>{test_compile_opts, [{src_dirs, ["dir"]}]}.</code>.
+%% <code>{eunit_compile_opts, [{src_dirs, ["src", "dir"]}]}.</code>.
 %% @copyright 2009, 2010 Dave Smith
 %% -------------------------------------------------------------------
 -module(rebar_eunit).
@@ -69,6 +69,9 @@
 -export([eunit/2,
          clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 -define(EUNIT_DIR, ".eunit").
@@ -100,6 +103,40 @@ clean(_Config, _File) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, eunit) ->
+    info_help("Run eunit tests");
+info(help, clean) ->
+    Description = ?FMT("Delete eunit test dir (~s)", [?EUNIT_DIR]),
+    info_help(Description).
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "Valid command line options:~n"
+       "  suites=\"foo,bar\" (Run tests in foo.erl, test/foo_tests.erl and~n"
+       "                    tests in bar.erl, test/bar_tests.erl)~n"
+       "  tests=\"baz\" (For every existing suite, run the first test whose~n"
+       "               name starts with bar and, if no such test exists,~n"
+       "               run the test whose name starts with bar in the~n"
+       "               suite's _tests module)~n",
+       [
+        Description,
+        {eunit_opts, []},
+        {eunit_compile_opts, []},
+        {eunit_first_files, []},
+        {cover_enabled, false},
+        {cover_print_enabled, false},
+        {cover_export_enabled, false}
+       ]).
+
 run_eunit(Config, CodePath, SrcErls) ->
     %% Build a list of all the .beams in ?EUNIT_DIR -- use this for
     %% cover and eunit testing. Normally you can just tell cover
diff --git a/src/rebar_lfe_compiler.erl b/src/rebar_lfe_compiler.erl
index d288ca5..2a047d8 100644
--- a/src/rebar_lfe_compiler.erl
+++ b/src/rebar_lfe_compiler.erl
@@ -30,6 +30,9 @@
 
 -export([compile/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -45,6 +48,14 @@ compile(Config, _AppFile) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, compile) ->
+    ?CONSOLE(
+       "Build Lisp Flavoured Erlang (*.lfe) sources.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  erl_opts is reused.'~n",
+       []).
+
 compile_lfe(Source, _Target, Config) ->
     case code:which(lfe_comp) of
         non_existing ->
diff --git a/src/rebar_neotoma_compiler.erl b/src/rebar_neotoma_compiler.erl
index 33f32e3..5607aa4 100644
--- a/src/rebar_neotoma_compiler.erl
+++ b/src/rebar_neotoma_compiler.erl
@@ -42,6 +42,9 @@
 
 -export([compile/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ============================================================================
@@ -60,6 +63,19 @@ compile(Config, _AppFile) ->
 %% Internal functions
 %% ============================================================================
 
+info(help, compile) ->
+    ?CONSOLE(
+       "Build Neotoma (*.peg) sources.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n",
+       [
+        {neotom_opts, [{doc_root, "src"},
+                       {out_dir, "src"},
+                       {source_ext, ".peg"},
+                       {module_ext, ""}]}
+       ]).
+
 neotoma_opts(Config) ->
     rebar_config:get(Config, neotoma_opts, []).
 
diff --git a/src/rebar_otp_app.erl b/src/rebar_otp_app.erl
index a62f584..6c52336 100644
--- a/src/rebar_otp_app.erl
+++ b/src/rebar_otp_app.erl
@@ -29,6 +29,9 @@
 -export([compile/2,
          clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -82,11 +85,26 @@ clean(_Config, File) ->
             ok
     end.
 
-
 %% ===================================================================
 %% Internal functions
 %% ===================================================================
 
+info(help, compile) ->
+    info_help("Validate .app file");
+info(help, clean) ->
+    info_help("Delete .app file if generated from .app.src").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n",
+       [
+        Description,
+        {validate_app_modules, true}
+       ]).
+
 preprocess(Config, AppSrcFile) ->
     case rebar_app_utils:load_app_file(Config, AppSrcFile) of
         {ok, Config1, AppName, AppData} ->
diff --git a/src/rebar_port_compiler.erl b/src/rebar_port_compiler.erl
index 06a79bc..36d741d 100644
--- a/src/rebar_port_compiler.erl
+++ b/src/rebar_port_compiler.erl
@@ -27,8 +27,11 @@
 -module(rebar_port_compiler).
 
 -export([compile/2,
-         clean/2,
-         setup_env/1]).
+         clean/2]).
+
+%% for internal use only
+-export([setup_env/1,
+         info/2]).
 
 -include("rebar.hrl").
 
@@ -149,6 +152,27 @@ setup_env(Config) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, compile) ->
+    info_help("Build port sources");
+info(help, clean) ->
+    info_help("Delete port build results").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n",
+       [
+        Description,
+        {port_env, [{"CFLAGS", "$CFLAGS -Ifoo"},
+                    {"freebsd", "LDFLAGS", "$LDFLAGS -lfoo"}]},
+        {port_specs, [{"priv/so_name.so", ["c_src/*.c"]},
+                      {"linux", "priv/hello_linux", ["c_src/hello_linux.c"]},
+                      {"linux", "priv/hello_linux", ["c_src/*.c"], [{env, []}]}]}
+       ]).
+
 setup_env(Config, ExtraEnv) ->
     %% Extract environment values from the config (if specified) and
     %% merge with the default for this operating system. This enables
diff --git a/src/rebar_protobuffs_compiler.erl b/src/rebar_protobuffs_compiler.erl
index 7ef58d6..579ecfb 100644
--- a/src/rebar_protobuffs_compiler.erl
+++ b/src/rebar_protobuffs_compiler.erl
@@ -29,6 +29,9 @@
 -export([compile/2,
          clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 %% ===================================================================
@@ -57,7 +60,6 @@ compile(Config, _AppFile) ->
             end
     end.
 
-
 clean(_Config, _AppFile) ->
     %% Get a list of generated .beam and .hrl files and then delete them
     Protos = rebar_utils:find_files("src", ".*\\.proto$"),
@@ -71,11 +73,24 @@ clean(_Config, _AppFile) ->
             delete_each(Targets)
     end.
 
-
 %% ===================================================================
 %% Internal functions
 %% ===================================================================
 
+info(help, compile) ->
+    info_help("Build Protobuffs (*.proto) sources");
+info(help, clean) ->
+    info_help("Delete Protobuffs (*.proto) build results").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  erl_opts is passed as compile_flags to "
+       "protobuffs_compile:scan_file/2~n",
+       [Description]).
+
 protobuffs_is_present() ->
     code:which(protobuffs_compile) =/= non_existing.
 
@@ -115,7 +130,7 @@ compile_each(Config, [{Proto, Beam, Hrl} | Rest]) ->
                     ok = rebar_file_utils:mv(Hrl, "include"),
                     ok;
                 Other ->
-                    ?ERROR("Protobuff compile of ~s failed: ~p\n",
+                    ?ERROR("Protobuffs compile of ~s failed: ~p\n",
                            [Proto, Other]),
                     ?FAIL
             end;
diff --git a/src/rebar_qc.erl b/src/rebar_qc.erl
index 09e48e4..826ba9a 100644
--- a/src/rebar_qc.erl
+++ b/src/rebar_qc.erl
@@ -28,6 +28,9 @@
 
 -export([qc/2, triq/2, eqc/2, clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 -define(QC_DIR, ".qc").
@@ -57,6 +60,19 @@ clean(_Config, _File) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, qc) ->
+    ?CONSOLE(
+       "Test QuickCheck properties.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  {qc_opts, [{qc_mod, module()}, Options]}~n"
+       "  ~p~n"
+       "  ~p~n",
+       [
+        {qc_compile_opts, []},
+        {qc_first_files, []}
+       ]).
+
 -define(TRIQ_MOD, triq).
 -define(EQC_MOD, eqc).
 
diff --git a/src/rebar_reltool.erl b/src/rebar_reltool.erl
index 3c9b728..18b0702 100644
--- a/src/rebar_reltool.erl
+++ b/src/rebar_reltool.erl
@@ -30,6 +30,9 @@
          overlay/2,
          clean/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 -include_lib("kernel/include/file.hrl").
 
@@ -80,6 +83,32 @@ clean(Config, ReltoolFile) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, generate) ->
+    info_help("Build release with reltool");
+info(help, clean) ->
+    info_help("Delete release");
+info(help, overlay) ->
+    info_help("Run reltool overlays only").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~n"
+       "Valid reltool.config options:~n"
+       "  {sys, []}~n"
+       "  {target_dir, \"target\"}~n"
+       "  {overlay_vars, \"overlay\"}~n"
+       "  {overlay, []}~n"
+       "Valid command line options:~n"
+       "  target_dir=target~n"
+       "  overlay_vars=VarsFile~n"
+       "  dump_spec=1 (write reltool target spec to reltool.spec)~n",
+       [
+        Description
+       ]).
+
 check_vsn() ->
     %% TODO: use application:load and application:get_key once we require
     %%       R14A or newer. There's no reltool.app before R14A.
diff --git a/src/rebar_require_vsn.erl b/src/rebar_require_vsn.erl
index 9a0a005..385f55c 100644
--- a/src/rebar_require_vsn.erl
+++ b/src/rebar_require_vsn.erl
@@ -33,6 +33,9 @@
 -export([compile/2,
          eunit/2]).
 
+%% for internal use only
+-export([info/2]).
+
 %% ===================================================================
 %% Public API
 %% ===================================================================
@@ -47,6 +50,25 @@ eunit(Config, _) ->
 %% Internal functions
 %% ====================================================================
 
+info(help, compile) ->
+    info_help();
+info(help, eunit) ->
+    info_help().
+
+info_help() ->
+    ?CONSOLE(
+       "Check required ERTS or OTP release version.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n",
+       [
+        {require_erts_vsn, ".*"},
+        {require_otp_vsn, ".*"},
+        {require_min_otp_vsn, ".*"}
+       ]).
+
 check_versions(Config) ->
     ErtsRegex = rebar_config:get(Config, require_erts_vsn, ".*"),
     ReOpts = [{capture, none}],
diff --git a/src/rebar_templater.erl b/src/rebar_templater.erl
index 0e1eef1..453f925 100644
--- a/src/rebar_templater.erl
+++ b/src/rebar_templater.erl
@@ -35,6 +35,9 @@
 -export([resolve_variables/2,
          render/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -include("rebar.hrl").
 
 -define(TEMPLATE_RE, ".*\\.template\$").
@@ -98,6 +101,27 @@ render(Bin, Context) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, create) ->
+    ?CONSOLE(
+       "Create skel based on template and vars.~n"
+       "~n"
+       "Valid command line options:~n"
+       "  template= [var=foo,...]~n", []);
+info(help, 'create-app') ->
+    ?CONSOLE(
+       "Create simple app skel.~n"
+       "~n"
+       "Valid command line options:~n"
+       "  [appid=myapp]~n", []);
+info(help, 'create-node') ->
+    ?CONSOLE(
+       "Create simple node skel.~n"
+       "~n"
+       "Valid command line options:~n"
+       "  [nodeid=mynode]~n", []);
+info(help, 'list-templates') ->
+    ?CONSOLE("List available templates.~n", []).
+
 create1(Config, TemplateId) ->
     {AvailTemplates, Files} = find_templates(Config),
     ?DEBUG("Available templates: ~p\n", [AvailTemplates]),
diff --git a/src/rebar_upgrade.erl b/src/rebar_upgrade.erl
index 14ea758..d18603c 100644
--- a/src/rebar_upgrade.erl
+++ b/src/rebar_upgrade.erl
@@ -32,6 +32,9 @@
 
 -export(['generate-upgrade'/2]).
 
+%% for internal use only
+-export([info/2]).
+
 -define(TMP, "_tmp").
 
 %% ====================================================================
@@ -80,6 +83,13 @@
 %% Internal functions
 %% ==================================================================
 
+info(help, 'generate-upgrade') ->
+    ?CONSOLE("Build an upgrade package.~n"
+             "~n"
+             "Valid command line options:~n"
+             "  previous_release=path~n",
+             []).
+
 run_checks(Config, OldVerPath, ReltoolConfig) ->
     true = rebar_utils:prop_check(filelib:is_dir(OldVerPath),
                                   "Release directory doesn't exist (~p)~n",
diff --git a/src/rebar_xref.erl b/src/rebar_xref.erl
index a55d71d..8c0a872 100644
--- a/src/rebar_xref.erl
+++ b/src/rebar_xref.erl
@@ -37,6 +37,9 @@
 
 -export([xref/2]).
 
+%% for internal use only
+-export([info/2]).
+
 %% ===================================================================
 %% Public API
 %% ===================================================================
@@ -100,6 +103,22 @@ xref(Config, _) ->
 %% Internal functions
 %% ===================================================================
 
+info(help, xref) ->
+    ?CONSOLE(
+       "Run cross reference analysis.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n",
+       [
+        {xref_warnings, false},
+        {xref_checks, [exports_not_used, undefined_function_calls]},
+        {xref_queries,
+         [{"(xc - uc) || (xu - x - b"
+           " - (\"mod\":\".*foo\"/\"4\"))",[]}]}
+       ]).
+
 check_exports_not_used() ->
     {ok, UnusedExports0} = xref:analyze(xref, exports_not_used),
     UnusedExports = filter_away_ignored(UnusedExports0),