Fix bug in AutoExpandReplicas.Create (#5260)

The create method was not allowing the valid value of "false.

Fixes #5258

Author: stevejgordon

src/Nest/IndexModules/IndexSettings/Settings/AutoExpandReplicas.cs

@@ -98,6 +98,9 @@ public static AutoExpandReplicas Create(string value)
 			if (value.IsNullOrEmpty())
 				throw new ArgumentException("cannot be null or empty", nameof(value));
 
+			if (value.Equals("false", StringComparison.OrdinalIgnoreCase))
+				return Disabled;
+			
 			var expandReplicaParts = value.Split('-');
 			if (expandReplicaParts.Length != 2)
 				throw new ArgumentException("must contain a 'from' and 'to' value", nameof(value));

tests/Tests/CommonOptions/AutoExpandReplicas/AutoExpandReplicasTests.cs

@@ -77,6 +77,17 @@ public void CreateWithMinAndAll()
 			autoExpandReplicas.ToString().Should().Be("0-all");
 		}
 
+		[U]
+		public void CreateWithFalse()
+		{
+			var autoExpandReplicas = Nest.AutoExpandReplicas.Create("false");
+			autoExpandReplicas.Should().NotBeNull();
+			autoExpandReplicas.Enabled.Should().BeFalse();
+			autoExpandReplicas.MinReplicas.Should().BeNull();
+			autoExpandReplicas.MaxReplicas.Should().BeNull();
+			autoExpandReplicas.ToString().Should().Be("false");
+		}
+
 		[U]
 		public void Disabled()
 		{