Move version check/enforcement for reltool into rebar_reltool; rebar should work (excepting reltool support) with anything as far back as R12, once you've compiled it

src/rebar.erl

@@ -29,26 +29,6 @@
 -export([main/1]).
 
 main(Args) ->
-    %% HACK: Make sure the caller is running w/ r13b03 and reltool >= 0.5.2
-    case erlang:system_info(version) < "5.7.4" of
-        true ->
-            io:format("Rebar requires at least erts 5.7.4; this VM is using ~s\n",
-                      [erlang:system_info(version)]),
-            halt(1);
-        false ->
-            ok
-    end,
-
-    ReltoolVsn = filename:basename(code:lib_dir(reltool)),
-    case ReltoolVsn < "reltool-0.5.2" of
-        true ->
-            io:format("Rebar requires at least reltool-0.5.2; this VM is using ~s\n",
-                      [ReltoolVsn]),
-            halt(1);
-        false ->
-            ok
-    end,
-
     case catch(rebar_core:run(Args)) of
         ok ->
             ok;

src/rebar_reltool.erl

@@ -38,6 +38,9 @@
 %% ===================================================================
 
 generate(Config, ReltoolFile) ->
+    %% Make sure we have decent version of reltool available
+    check_vsn(),
+
     %% Load the reltool configuration from the file
     ReltoolConfig = load_config(ReltoolFile),
 
@@ -72,6 +75,21 @@ clean(_Config, ReltoolFile) ->
 %% Internal functions
 %% ===================================================================
 
+check_vsn() ->
+    case code:lib_dir(reltool) of
+        {error, bad_name} ->
+            ?ABORT("Reltool support requires the reltool application to be installed!", []);
+        Path ->
+            ReltoolVsn = filename:basename(Path),
+            case ReltoolVsn < "reltool-0.5.2" of
+                true ->
+                    ?ABORT("Reltool support requires at least reltool-0.5.2; this VM is using ~s\n",
+                           [ReltoolVsn]);
+                false ->
+                    ok
+            end
+    end.
+
 %%
 %% Load terms from reltool.config
 %%