Allow specification of module dependencies for appups

The order in which modules, within an application, are loaded can be
important. This patch adds allows the specification of module
dependencies such that generate .appup/.relup scripts will load a
module's dependent modules before itself.

To use:

in rebar.config, add a module_deps

{module_deps, [{ModuleName, [DependentModuleName, ...]}]}.

ModuleName is the name of any module, followed by a list of module
names that it depends on.

src/rebar_appups.erl

@@ -50,6 +50,8 @@
     PrevRelPath = rebar_rel_utils:get_previous_release_path(Config),
     OldVerPath = filename:join([TargetParentDir, PrevRelPath]),
 
+    ModDeps = rebar_config:get(Config, module_deps, []),
+
     %% Get the new and old release name and versions
     {Name, _Ver} = rebar_rel_utils:get_reltool_release_info(ReltoolConfig),
     NewVerPath = filename:join([TargetParentDir, Name]),
@@ -77,7 +79,7 @@
     UpgradeApps = genappup_which_apps(Upgraded, AppUpApps),
 
     %% Generate appup files for upgraded apps
-    generate_appup_files(NewVerPath, OldVerPath, UpgradeApps),
+    generate_appup_files(NewVerPath, OldVerPath, ModDeps, UpgradeApps),
 
     {ok, Config1}.
 
@@ -139,9 +141,9 @@ genappup_which_apps(UpgradedApps, [First|Rest]) ->
 genappup_which_apps(Apps, []) ->
     Apps.
 
-generate_appup_files(NewVerPath, OldVerPath, [{_App, {undefined, _}}|Rest]) ->
-    generate_appup_files(NewVerPath, OldVerPath, Rest);
-generate_appup_files(NewVerPath, OldVerPath, [{App, {OldVer, NewVer}}|Rest]) ->
+generate_appup_files(NewVerPath, OldVerPath, ModDeps, [{_App, {undefined, _}}|Rest]) ->
+    generate_appup_files(NewVerPath, OldVerPath, ModDeps, Rest);
+generate_appup_files(NewVerPath, OldVerPath, ModDeps, [{App, {OldVer, NewVer}}|Rest]) ->
     OldEbinDir = filename:join([OldVerPath, "lib",
                                 atom_to_list(App) ++ "-" ++ OldVer, "ebin"]),
     NewEbinDir = filename:join([NewVerPath, "lib",
@@ -150,9 +152,14 @@ generate_appup_files(NewVerPath, OldVerPath, [{App, {OldVer, NewVer}}|Rest]) ->
     {AddedFiles, DeletedFiles, ChangedFiles} = beam_lib:cmp_dirs(NewEbinDir,
                                                                  OldEbinDir),
 
+    ChangedNames = [list_to_atom(file_to_name(F)) || {F, _} <- ChangedFiles],
+    ModDeps1 = [{N, [M1 || M1 <- M, lists:member(M1, ChangedNames)]}
+                || {N, M} <- ModDeps],
+
     Added = [generate_instruction(added, File) || File <- AddedFiles],
     Deleted = [generate_instruction(deleted, File) || File <- DeletedFiles],
-    Changed = [generate_instruction(changed, File) || File <- ChangedFiles],
+    Changed = [generate_instruction(changed, ModDeps1, File)
+               || File <- ChangedFiles],
 
     Inst = lists:append([Added, Deleted, Changed]),
 
@@ -164,8 +171,8 @@ generate_appup_files(NewVerPath, OldVerPath, [{App, {OldVer, NewVer}}|Rest]) ->
                                         OldVer, Inst, OldVer])),
 
     ?CONSOLE("Generated appup for ~p~n", [App]),
-    generate_appup_files(NewVerPath, OldVerPath, Rest);
-generate_appup_files(_, _, []) ->
+    generate_appup_files(NewVerPath, OldVerPath, ModDeps, Rest);
+generate_appup_files(_, _, _, []) ->
     ?CONSOLE("Appup generation complete~n", []).
 
 generate_instruction(added, File) ->
@@ -173,25 +180,27 @@ generate_instruction(added, File) ->
     {add_module, Name};
 generate_instruction(deleted, File) ->
     Name = list_to_atom(file_to_name(File)),
-    {delete_module, Name};
-generate_instruction(changed, {File, _}) ->
+    {delete_module, Name}.
+
+generate_instruction(changed, ModDeps, {File, _}) ->
     {ok, {Name, List}} = beam_lib:chunks(File, [attributes, exports]),
     Behavior = get_behavior(List),
     CodeChange = is_code_change(List),
-    generate_instruction_advanced(Name, Behavior, CodeChange).
+    Deps = proplists:get_value(Name, ModDeps, []),
+    generate_instruction_advanced(Name, Behavior, CodeChange, Deps).
 
-generate_instruction_advanced(Name, undefined, undefined) ->
+generate_instruction_advanced(Name, undefined, undefined, Deps) ->
     %% Not a behavior or code change, assume purely functional
-    {load_module, Name};
-generate_instruction_advanced(Name, [supervisor], _) ->
+    {load_module, Name, Deps};
+generate_instruction_advanced(Name, [supervisor], _, _) ->
     %% Supervisor
     {update, Name, supervisor};
-generate_instruction_advanced(Name, _, code_change) ->
+generate_instruction_advanced(Name, _, code_change, Deps) ->
     %% Includes code_change export
-    {update, Name, {advanced, []}};
-generate_instruction_advanced(Name, _, _) ->
+    {update, Name, {advanced, []}, Deps};
+generate_instruction_advanced(Name, _, _, Deps) ->
     %% Anything else
-    {load_module, Name}.
+    {load_module, Name, Deps}.
 
 get_behavior(List) ->
     Attributes = proplists:get_value(attributes, List),