ProgressTask.GetPercentage() returns 100 when max value is 0 (#1694)

src/Spectre.Console/Live/Progress/ProgressTask.cs

@@ -224,6 +224,11 @@ public sealed class ProgressTask : IProgress<double>
 
     private double GetPercentage()
     {
+        if (MaxValue == 0)
+        {
+            return 100;
+        }
+
         var percentage = (Value / MaxValue) * 100;
         percentage = Math.Min(100, Math.Max(0, percentage));
         return percentage;

src/Tests/Spectre.Console.Tests/Unit/Live/Progress/ProgressTests.cs

@@ -118,6 +118,31 @@ public sealed class ProgressTests
         task.Value.ShouldBe(20);
     }
 
+    [Fact]
+    public void Setting_Max_Value_To_Zero_Should_Make_Percentage_OneHundred()
+    {
+        // Given
+        var console = new TestConsole()
+            .Interactive();
+
+        var task = default(ProgressTask);
+        var progress = new Progress(console)
+            .Columns(new[] { new ProgressBarColumn() })
+            .AutoRefresh(false)
+            .AutoClear(false);
+
+        // When
+        progress.Start(ctx =>
+        {
+            task = ctx.AddTask("foo");
+            task.MaxValue = 0;
+        });
+
+        // Then
+        task.Value.ShouldBe(0);
+        task.Percentage.ShouldBe(100);
+    }
+
     [Fact]
     public void Setting_Value_Should_Override_Incremented_Value()
     {