Fix formatting of 0.0 with (#1210)

include/fmt/format-inl.h

@@ -685,7 +685,7 @@ FMT_API bool grisu_format(Double value, buffer<char>& buf, int precision,
   FMT_ASSERT(value >= 0, "value is negative");
   bool fixed = (options & grisu_options::fixed) != 0;
   if (value <= 0) {  // <= instead of == to silence a warning.
-    if (precision < 0 || !fixed) {
+    if (precision <= 0 || !fixed) {
       exp = 0;
       buf.push_back('0');
     } else {

test/format-test.cc

@@ -1452,6 +1452,7 @@ TEST(FormatterTest, FormatDouble) {
 }
 
 TEST(FormatterTest, PrecisionRounding) {
+  EXPECT_EQ("0", format("{:.0f}", 0.0));
   EXPECT_EQ("0", format("{:.0f}", 0.1));
   EXPECT_EQ("0.000", format("{:.3f}", 0.00049));
   EXPECT_EQ("0.001", format("{:.3f}", 0.0005));