Generate .hrl file from .mib

Generate .hrl files into include from SNMP MIB files.
Change the order of so .mib files are built before .erl
This is necessary since .hrl files are generated from
the .mib files.
The generated .bin and .hrl files are deleted by clean.

This is a cleaned up version of a patch originally
sent to the rebar mailing list by David Nonnenmacher.

src/rebar_erlc_compiler.erl

@@ -87,15 +87,19 @@ compile(Config, _AppFile) ->
                                           Config, yrl_first_files, [])),
                             "src", ".yrl", "src", ".erl",
                             fun compile_yrl/3),
-    doterl_compile(Config, "ebin"),
     rebar_base_compiler:run(Config,
                             check_files(rebar_config:get_local(
                                           Config, mib_first_files, [])),
                             "mibs", ".mib", "priv/mibs", ".bin",
-                            fun compile_mib/3).
+                            fun compile_mib/3),
+    doterl_compile(Config, "ebin").
 
 -spec clean(Config::rebar_config:config(), AppFile::file:filename()) -> 'ok'.
 clean(_Config, _AppFile) ->
+    MibFiles = rebar_utils:find_files("mibs", "^.*\\.mib\$"),
+    MIBs = [filename:rootname(filename:basename(MIB)) || MIB <- MibFiles],
+    rebar_file_utils:delete_each(
+      [filename:join(["include",MIB++".hrl"]) || MIB <- MIBs]),
     lists:foreach(fun(F) -> ok = rebar_file_utils:rm_rf(F) end,
                   ["ebin/*.beam", "priv/mibs/*.bin"]),
 
@@ -270,6 +274,10 @@ compile_mib(Source, Target, Config) ->
         rebar_config:get(Config, mib_opts, []),
     case snmpc:compile(Source, Opts) of
         {ok, _} ->
+            Mib = filename:rootname(Target),
+            ok = snmpc:mib_to_hrl(Mib),
+            Hrl_filename = Mib ++ ".hrl",
+            rebar_file_utils:mv(Hrl_filename,"include"),
             ok;
         {error, compilation_failed} ->
             ?FAIL