Change number_to_currency behavior for checking negativity

- Instead of using `to_f.phase`, just use `to_f.negative`?.
- This change works same for all cases except when number is "-0.0".
      -0.0.to_f.negative? => false
      -0.0.to_f.phase? => pi
- So -0.0 will be treated as positive from now onwards.
- So this change reverts changes from https://github.com/rails/rails/pull/6512.
- But it should be acceptable as we could not find any currency which
  supports negative zeros.

activesupport/CHANGELOG.md

+*   Change number_to_currency behavior for checking negativity.
+
+    Used `to_f.negative` instead of using `to_f.phase` for checking negativity
+    of a number in number_to_currency helper.
+    This change works same for all cases except when number is "-0.0".
+
+        -0.0.to_f.negative? => false
+        -0.0.to_f.phase? => 3.14
+
+    This change reverts changes from https://github.com/rails/rails/pull/6512.
+    But it should be acceptable as we could not find any currency which
+    supports negative zeros.
+
+    *Prathamesh Sonpatki*, *Rafael Mendonça França*
+
 *   Match `HashWithIndifferentAccess#default`'s behaviour with `Hash#default`.
 
     *David Cornu*

activesupport/lib/active_support/number_helper/number_to_currency_converter.rb

@@ -7,7 +7,7 @@ def convert
         number = self.number.to_s.strip
         format = options[:format]
 
-        if is_negative?(number)
+        if number.to_f.negative?
           format = options[:negative_format]
           number = absolute_value(number)
         end
@@ -18,10 +18,6 @@ def convert
 
       private
 
-        def is_negative?(number)
-          number.to_f.phase != 0
-        end
-
         def absolute_value(number)
           number.respond_to?(:abs) ? number.abs : number.sub(/\A-/, '')
         end

activesupport/test/number_helper_test.rb

@@ -74,7 +74,6 @@ def test_number_to_currency
           assert_equal("1,234,567,890.50 Kč", number_helper.number_to_currency("1234567890.50", {:unit => "Kč", :format => "%n %u"}))
           assert_equal("1,234,567,890.50 - Kč", number_helper.number_to_currency("-1234567890.50", {:unit => "Kč", :format => "%n %u", :negative_format => "%n - %u"}))
           assert_equal("0.00", number_helper.number_to_currency(+0.0, {:unit => "", :negative_format => "(%n)"}))
-          assert_equal("(0.00)", number_helper.number_to_currency(-0.0, {:unit => "", :negative_format => "(%n)"}))
         end
       end