From 9c23dfef72c381d93e3d7843700a2e9949c6e31e Mon Sep 17 00:00:00 2001
From: Tino Breddin <dev.can.i@gmail.com>
Date: Thu, 20 Feb 2014 10:56:37 +0100
Subject: [PATCH] Add REBAR to environment before executing hooks

REBAR will be set to the rebar binary which was executed and runs the
builds. Enables the use of the same binary for rebar invocations as
part of a pre or post hook like so:

    ${REBAR} escriptize
---
 src/rebar_core.erl  |  3 ++-
 src/rebar_utils.erl | 20 +++++++++++++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/rebar_core.erl b/src/rebar_core.erl
index 3a4f205..212365b 100644
--- a/src/rebar_core.erl
+++ b/src/rebar_core.erl
@@ -496,8 +496,9 @@ run_modules([Module | Rest], Command, Config, File) ->
             {Module, Error}
     end.
 
-apply_hooks(Mode, Config, Command, Env) ->
+apply_hooks(Mode, Config, Command, Env0) ->
     Hooks = rebar_config:get_local(Config, Mode, []),
+    Env = rebar_utils:patch_env(Config, Env0),
     lists:foreach(fun apply_hook/1,
                   [{Env, Hook} || Hook <- Hooks,
                                   element(1, Hook) =:= Command orelse
diff --git a/src/rebar_utils.erl b/src/rebar_utils.erl
index 517ac33..5520656 100644
--- a/src/rebar_utils.erl
+++ b/src/rebar_utils.erl
@@ -53,7 +53,8 @@
          src_dirs/1,
          ebin_dir/0,
          base_dir/1,
-         processing_base_dir/1, processing_base_dir/2]).
+         processing_base_dir/1, processing_base_dir/2,
+         patch_env/2]).
 
 -include("rebar.hrl").
 
@@ -319,6 +320,23 @@ processing_base_dir(Config, Dir) ->
     AbsDir = filename:absname(Dir),
     AbsDir =:= base_dir(Config).
 
+%% @doc Returns the list of environment variables including 'REBAR' which points to the
+%% rebar executable used to execute the currently running command. The environment is
+%% not modified if rebar was invoked programmatically.
+-spec patch_env(rebar_config:config(), [{string(), string()}]) -> [{string(), string()}].
+patch_env(Config, []) ->
+    % if we reached an empty list the env did not contain the REBAR variable
+    case rebar_config:get_xconf(Config, escript, "") of
+        "" -> % rebar was invoked programmatically
+            [];
+        Path ->
+            [{"REBAR", Path}]
+    end;
+patch_env(_Config, [{"REBAR", _} | _]=All) ->
+    All;
+patch_env(Config, [E | Rest]) ->
+    [E | patch_env(Config, Rest)].
+
 %% ====================================================================
 %% Internal functions
 %% ====================================================================