fix bootstrap on windows, fallback to copy if symlinking fails

bootstrap

@@ -2,6 +2,7 @@
 %% -*- mode: erlang;erlang-indent-level: 4;indent-tabs-mode: nil -*-
 %% ex: ft=erlang ts=4 sw=4 et
 
+
 main(_Args) ->
     %% Fetch and build deps required to build rebar3
     BaseDeps = [{providers, []}
@@ -105,12 +106,105 @@ compile_file(File, Opts) ->
 bootstrap_rebar3() ->
     filelib:ensure_dir("_build/default/lib/rebar/ebin/dummy.beam"),
     code:add_path("_build/default/lib/rebar/ebin/"),
-    file:make_symlink(filename:absname("src"), filename:absname("_build/default/lib/rebar/src")),
+    ok = symlink_or_copy(filename:absname("src"),
+                         filename:absname("_build/default/lib/rebar/src")),
     Sources = ["src/rebar_resource.erl" | filelib:wildcard("src/*.erl")],
     [compile_file(X, [{outdir, "_build/default/lib/rebar/ebin/"}
                      ,return | additional_defines()]) || X <- Sources],
     code:add_patha(filename:absname("_build/default/lib/rebar/ebin")).
 
+%%rebar.hrl
+-define(FMT(Str, Args), lists:flatten(io_lib:format(Str, Args))).
+%%/rebar.hrl
+%%rebar_file_utils
+symlink_or_copy(Source, Target) ->
+    Link = case os:type() of
+               {win32, _} ->
+                   Source;
+               _ ->
+                   rebar_dir:make_relative_path(Source, Target)
+           end,
+    case file:make_symlink(Link, Target) of
+        ok ->
+            ok;
+        {error, eexist} ->
+            ok;
+        {error, _} ->
+            cp_r([Source], Target)
+    end.
+
+cp_r([], _Dest) ->
+    ok;
+cp_r(Sources, Dest) ->
+    case os:type() of
+        {unix, _} ->
+            EscSources = [escape_path(Src) || Src <- Sources],
+            SourceStr = string:join(EscSources, " "),
+            os:cmd(?FMT("cp -R ~s \"~s\"", [SourceStr, Dest])),
+            ok;
+        {win32, _} ->
+            lists:foreach(fun(Src) -> ok = cp_r_win32(Src,Dest) end, Sources),
+            ok
+    end.
+
+xcopy_win32(Source,Dest)->
+    R = os:cmd(?FMT("xcopy \"~s\" \"~s\" /q /y /e 2> nul",
+                     [filename:nativename(Source), filename:nativename(Dest)])),
+    case length(R) > 0 of
+        %% when xcopy fails, stdout is empty and and error message is printed
+        %% to stderr (which is redirected to nul)
+        true -> ok;
+        false ->
+            {error, lists:flatten(
+                      io_lib:format("Failed to xcopy from ~s to ~s~n",
+                                    [Source, Dest]))}
+    end.
+
+cp_r_win32({true, SourceDir}, {true, DestDir}) ->
+    %% from directory to directory
+    SourceBase = filename:basename(SourceDir),
+    ok = case file:make_dir(filename:join(DestDir, SourceBase)) of
+             {error, eexist} -> ok;
+             Other -> Other
+         end,
+    ok = xcopy_win32(SourceDir, filename:join(DestDir, SourceBase));
+cp_r_win32({false, Source} = S,{true, DestDir}) ->
+    %% from file to directory
+    cp_r_win32(S, {false, filename:join(DestDir, filename:basename(Source))});
+cp_r_win32({false, Source},{false, Dest}) ->
+    %% from file to file
+    {ok,_} = file:copy(Source, Dest),
+    ok;
+cp_r_win32({true, SourceDir}, {false, DestDir}) ->
+    case filelib:is_regular(DestDir) of
+        true ->
+            %% From directory to file? This shouldn't happen
+            {error, lists:flatten(
+                      io_lib:format("Cannot copy dir (~p) to file (~p)\n",
+                                    [SourceDir, DestDir]))};
+        false ->
+            %% Specifying a target directory that doesn't currently exist.
+            %% So let's attempt to create this directory
+            case filelib:ensure_dir(filename:join(DestDir, "dummy")) of
+                ok ->
+                    ok = xcopy_win32(SourceDir, DestDir);
+                {error, Reason} ->
+                    {error, lists:flatten(
+                              io_lib:format("Unable to create dir ~p: ~p\n",
+                                            [DestDir, Reason]))}
+            end
+    end;
+cp_r_win32(Source,Dest) ->
+    Dst = {filelib:is_dir(Dest), Dest},
+    lists:foreach(fun(Src) ->
+                          ok = cp_r_win32({filelib:is_dir(Src), Src}, Dst)
+                  end, filelib:wildcard(Source)),
+    ok.
+
+escape_path(Str) ->
+    re:replace(Str, "([ ()?])", "\\\\&", [global, {return, list}]).
+%%/rebar_file_utils
+
 setup_env() ->
     %% We don't need or want relx providers loaded yet
     application:load(rebar),