in the prepare release the parameter "commitMessagePattern" should ha…

…ve as default value "{0}" before the default was null and had error on some unit test

src/NerdBank.GitVersioning/ReleaseManager.cs

@@ -130,7 +130,7 @@ public enum ReleaseManagerOutputMode
     /// <param name="commitMessagePattern">
     /// Custom pattern to add a prefix or suffix to the default commit message.
     /// </param>
-    public void PrepareRelease(string projectDirectory, string releaseUnstableTag = null, Version nextVersion = null, VersionOptions.ReleaseVersionIncrement? versionIncrement = null, ReleaseManagerOutputMode outputMode = default, string commitMessagePattern = null)
+    public void PrepareRelease(string projectDirectory, string releaseUnstableTag = null, Version nextVersion = null, VersionOptions.ReleaseVersionIncrement? versionIncrement = null, ReleaseManagerOutputMode outputMode = default, string commitMessagePattern = "{0}")
     {
         Requires.NotNull(projectDirectory, nameof(projectDirectory));
 

src/nbgv/Program.cs

@@ -768,11 +768,6 @@ private static Task<int> OnPrepareReleaseCommand(string project, string nextVers
             }
 
             // validate commit message pattern
-            if (string.IsNullOrEmpty(commitMessagePattern))
-            {
-                commitMessagePattern = "{0}";
-            }
-
             if (AreCurlyBracesBalanced(commitMessagePattern))
             {
                 Console.Error.WriteLine("Commit message pattern contains unbalanced curly braces.");