Add CommandSet helper to retrieve top level items

SabreTools.CommandLine.Test/CommandSetTests.cs

@@ -49,6 +49,28 @@ namespace SabreTools.CommandLine.Test
             Assert.Empty(actualName3);
         }
 
+        [Fact]
+        public void GetTopLevelTest()
+        {
+            var input1 = new FlagInput("input1", "--input1", "input1");
+            var input2 = new FlagInput("input2", "--input2", "input2");
+
+            var featureSet = new CommandSet();
+            featureSet.Add(input1);
+            featureSet.Add(input2);
+
+            var actualInput1 = featureSet.GetTopLevel("input1");
+            Assert.NotNull(actualInput1);
+            Assert.Equal("input1", actualInput1.Name);
+
+            var actualInput2 = featureSet.GetTopLevel("--input2");
+            Assert.NotNull(actualInput2);
+            Assert.Equal("input2", actualInput2.Name);
+
+            var actualInput3 = featureSet.GetTopLevel("input3");
+            Assert.Null(actualInput3);
+        }
+
         [Fact]
         public void TopLevelFlagTest()
         {

SabreTools.CommandLine/CommandSet.cs

@@ -127,6 +127,25 @@ namespace SabreTools.CommandLine
             return string.Empty;
         }
 
+        /// <summary>
+        /// Gets the top-level user input associated with a given name or flag
+        /// </summary>
+        /// <param name="value">Name or flag value to match</param>
+        /// <returns>User input associated with the name or flag, if possible</returns>
+        public UserInput? GetTopLevel(string value)
+        {
+            // Validate the value matches something
+            string inputName = GetInputName(value);
+            if (inputName.Length == 0)
+                return null;
+
+            // Try to get the child based on the name
+            if (!_inputs.TryGetValue(inputName, out var input))
+                return null;
+
+            return input;
+        }
+
         /// <summary>
         /// Check if a flag is a top-level (main application) flag
         /// </summary>