Honor $MaximumHistoryCount

This history count was being ignored, and the default in
PSReadline was 1024 instead of 4096 that PowerShell defaults
to.

The fix is to up the default, and safely set MaximumHistoryCount
in PSReadline based on the variable when initializing the first
time PSReadlne is called.

Fixes #135

Author: lzybkr

PSReadLine/Cmdlets.cs

@@ -69,7 +69,7 @@ public class PSConsoleReadlineOptions
         /// <summary>
         /// The maximum number of commands to store in the history.
         /// </summary>
-        public const int DefaultMaximumHistoryCount = 1024;
+        public const int DefaultMaximumHistoryCount = 4096;
 
         /// <summary>
         /// The maximum number of items to store in the kill ring.

PSReadLine/PSReadLine.psm1

@@ -22,6 +22,15 @@ function PSConsoleHostReadline
         $script:firstTime = $false
 
         $options = [PSConsoleUtilities.PSConsoleReadLine]::GetOptions()
+
+        # Honor $MaximumHistoryCount, but get it safely in case it was removed in the profile.
+        $MaximumHistoryCount = Get-Variable -ea Ignore -ValueOnly MaximumHistoryCount
+        if ($MaximumHistoryCount -gt 0)
+        {
+            $options.MaximumHistoryCount = $MaximumHistoryCount
+            [PSConsoleUtilities.PSConsoleReadLine]::SetOptions($options)
+        }
+
         if ($options.HistorySaveStyle -eq [PSConsoleUtilities.HistorySaveStyle]::SaveNothing)
         {
             # PSReadline isn't saving history, but we might still have history to reuse