Fix piping more than one CommandInfo to Get-Command (PowerShell#10929)

Author: SteveL-MSFT

src/System.Management.Automation/engine/GetCommandCommand.cs

@@ -390,6 +390,8 @@ protected override void BeginProcessing()
         /// </summary>
         protected override void ProcessRecord()
         {
+            _commandsWritten.Clear();
+
             // Module and FullyQualifiedModule should not be specified at the same time.
             // Throw out terminating error if this is the case.
             if (_isModuleSpecified && _isFullyQualifiedModuleSpecified)

test/powershell/Modules/Microsoft.PowerShell.Core/Get-Command.Tests.ps1

@@ -263,4 +263,10 @@ Describe "Get-Command Tests" -Tags "CI" {
         VerifyDynamicParametersExist -cmdlet $results[0] -parameterNames $paramName
         VerifyParameterType -cmdlet $results[0] -parameterName $paramName -ParameterType System.Text.Encoding
     }
+
+    It "Piping more than one CommandInfo works" {
+        $result = Get-Command -Name Add-Content, Get-Content | Get-Command
+        $result.Count | Should -Be 2
+        $result.Name | Should -Be "Add-Content","Get-Content"
+    }
 }