fix dirs robocopy and canonical paths in windows

- robocopying a directory into another directory recursively expects the
  directory name to be properly mapped onto the destination, otherwise
  all the files are copied into the given path. This patches things so
  a directory-to-directory robocopy works as expected in a linux mindset
  so tests pass
- the test for canonical paths didn't expect a windows environment at
  all; the test (and library) is modified to be consistent in that
  environment: always with a native format and with proper support of
  drive letters.

src/rebar_file_utils.erl

@@ -262,9 +262,11 @@ path_from_ancestor_(_, _)                     -> {error, badparent}.
 %% reduce a filepath by removing all incidences of `.' and `..'
 -spec canonical_path(string()) -> string().
 
-canonical_path(Dir) -> canonical_path([], filename:split(filename:absname(Dir))).
+canonical_path(Dir) ->
+    Canon = canonical_path([], filename:split(filename:absname(Dir))),
+    filename:nativename(Canon).
 
-canonical_path([], [])                -> filename:nativename("/");
+canonical_path([], [])                -> filename:absname("/");
 canonical_path(Acc, [])               -> filename:join(lists:reverse(Acc));
 canonical_path(Acc, ["."|Rest])       -> canonical_path(Acc, Rest);
 canonical_path([_|Acc], [".."|Rest])  -> canonical_path(Acc, Rest);
@@ -283,13 +285,19 @@ delete_each_dir_win32([Dir | Rest]) ->
     delete_each_dir_win32(Rest).
 
 xcopy_win32(Source,Dest)->
-    %% "xcopy \"~s\" \"~s\" /q /y /e 2> nul", Chanegd to robocopy to
+    %% "xcopy \"~s\" \"~s\" /q /y /e 2> nul", Changed to robocopy to
     %% handle long names. May have issues with older windows.
     Cmd = case filelib:is_dir(Source) of
               true ->
+                  %% For robocopy, copying /a/b/c/ to /d/e/f/ recursively does not
+                  %% create /d/e/f/c/*, but rather copies all files to /d/e/f/*.
+                  %% The usage we make here expects the former, not the later, so we
+                  %% must manually add the last fragment of a directory to the `Dest`
+                  %% in order to properly replicate POSIX platforms
+                  NewDest = filename:join([Dest, filename:basename(Source)]),
                   ?FMT("robocopy \"~s\" \"~s\" /e /is 1> nul",
                        [rebar_utils:escape_double_quotes(filename:nativename(Source)),
-                        rebar_utils:escape_double_quotes(filename:nativename(Dest))]);
+                        rebar_utils:escape_double_quotes(filename:nativename(NewDest))]);
               false ->
                   ?FMT("robocopy \"~s\" \"~s\" \"~s\" /e /is 1> nul",
                        [rebar_utils:escape_double_quotes(filename:nativename(filename:dirname(Source))),

test/rebar_file_utils_SUITE.erl

@@ -97,10 +97,17 @@ path_from_ancestor(_Config) ->
     ?assertEqual({error, badparent}, rebar_file_utils:path_from_ancestor("/foo/bar/baz", "/foo/bar/baz/qux")).
 
 canonical_path(_Config) ->
-    ?assertEqual(filename:nativename("/"), rebar_file_utils:canonical_path("/")),
-    ?assertEqual(filename:nativename("/"), rebar_file_utils:canonical_path("/../../..")),
-    ?assertEqual("/foo", rebar_file_utils:canonical_path("/foo/bar/..")),
-    ?assertEqual("/foo", rebar_file_utils:canonical_path("/foo/../foo")),
-    ?assertEqual("/foo", rebar_file_utils:canonical_path("/foo/.")),
-    ?assertEqual("/foo", rebar_file_utils:canonical_path("/foo/./.")),
-    ?assertEqual("/foo/bar", rebar_file_utils:canonical_path("/foo/./bar")).
+    %% We find the root so that the name works both on unix-likes and
+    %% with Windows.
+    Root = case os:type() of
+               {win32, _} -> filename:nativename(filename:absname("/")); % C:\, with proper drive
+               _ -> "/"
+           end,
+    ?assertEqual(filename:nativename(Root), rebar_file_utils:canonical_path("/")),
+    ?assertEqual(filename:nativename(Root), rebar_file_utils:canonical_path("/../../..")),
+    ?assertEqual(Root ++ "foo", rebar_file_utils:canonical_path("/foo/bar/..")),
+    ?assertEqual(Root ++ "foo", rebar_file_utils:canonical_path("/foo/../foo")),
+    ?assertEqual(Root ++ "foo", rebar_file_utils:canonical_path("/foo/.")),
+    ?assertEqual(Root ++ "foo", rebar_file_utils:canonical_path("/foo/./.")),
+    ?assertEqual(filename:nativename(Root ++ "foo/bar"),
+                 rebar_file_utils:canonical_path("/foo/./bar")).