[Yaml] Wrap numeric strings in quotes when dumping

This addresses an obscure case where a hash string (actually a commit-ish, "686e444") was dumped to YAML as an unquoted string value. It was later parsed from YAML as an exponential numeric and changed to ".Inf".

src/Symfony/Component/Yaml/Inline.php

@@ -87,7 +87,7 @@ class Inline
             case ctype_digit($value):
                 return is_string($value) ? "'$value'" : (int) $value;
             case is_numeric($value):
-                return is_infinite($value) ? str_ireplace('INF', '.Inf', strval($value)) : (is_string($value) ? "'$value'" : $value);
+                return is_string($value) ? "'$value'" : (is_infinite($value) ? str_ireplace('INF', '.Inf', strval($value)) : $value);
             case Escaper::requiresDoubleQuoting($value):
                 return Escaper::escapeWithDoubleQuotes($value);
             case Escaper::requiresSingleQuoting($value):

tests/Symfony/Tests/Component/Yaml/InlineTest.php

@@ -48,6 +48,13 @@ class InlineTest extends \PHPUnit_Framework_TestCase
         }
     }
 
+    public function testHashStringsResemblingExponentialNumericsShouldNotBeChangedToINF()
+    {
+        $value = '686e444';
+
+        $this->assertSame($value, Inline::parse(Inline::dump($value)));
+    }
+
     protected function getTestsForParse()
     {
         return array(
@@ -63,6 +70,8 @@ class InlineTest extends \PHPUnit_Framework_TestCase
             '02333' => 02333,
             '.Inf' => -log(0),
             '-.Inf' => log(0),
+            "'686e444'" => '686e444',
+            '686e444' => 646e444,
             '123456789123456789' => '123456789123456789',
             '"foo\r\nbar"' => "foo\r\nbar",
             "'foo#bar'" => 'foo#bar',
@@ -121,6 +130,8 @@ class InlineTest extends \PHPUnit_Framework_TestCase
             '1243' => 02333,
             '.Inf' => -log(0),
             '-.Inf' => log(0),
+            "'686e444'" => '686e444',
+            '.Inf' => 646e444,
             '"foo\r\nbar"' => "foo\r\nbar",
             "'foo#bar'" => 'foo#bar',
             "'foo # bar'" => 'foo # bar',