ignore non-positive max width in HelpBuilder.ctor

Author: adamralph

src/System.CommandLine.Tests/Help/HelpBuilderTests.cs

@@ -1638,10 +1638,10 @@ public void Help_describes_default_values_for_subcommand_with_multiple_defaultab
         [InlineData(0)]
         [InlineData(-1)]
         [InlineData(int.MinValue)]
-        public void Constructor_max_width_must_be_positive(int maxWidth)
+        public void Constructor_ignores_non_positive_max_width(int maxWidth)
         {
-            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => new HelpBuilder(_console, maxWidth));
-            Assert.Equal("maxWidth", ex.ParamName);
+            var helpBuilder = new HelpBuilder(_console, maxWidth);
+            Assert.Equal(int.MaxValue, helpBuilder.MaxWidth);
         }
 
         private class CustomHelpBuilderThatAddsTextAfterDefaultText : HelpBuilder

src/System.CommandLine/Help/HelpBuilder.cs

@@ -22,7 +22,7 @@ public class HelpBuilder : IHelpBuilder
         public HelpBuilder(IConsole console, int maxWidth = int.MaxValue)
         {
             Console = console ?? throw new ArgumentNullException(nameof(console));
-            if (maxWidth <= 0) throw new ArgumentOutOfRangeException(nameof(maxWidth), "Max width must be positive");
+            if (maxWidth <= 0) maxWidth = int.MaxValue;
             MaxWidth = maxWidth;
         }