perf: unnecessary exceptions when checking if a project is versionable (

#106)

In the case of checking whether a project can be versioned,
the invalid operation exception is swallowed because it is
not really invalid for that use case.  This update only
builds the exception for the Create case and so skips the
cost of the exception in the more common case

Versionize/Project.cs

@@ -16,7 +16,12 @@ private Project(string projectFile, SemanticVersion version)
 
     public static Project Create(string projectFile)
     {
-        var version = ReadVersion(projectFile);
+        var (success,version, error) = ReadVersion(projectFile);
+
+        if (!success)
+        {
+            throw new InvalidOperationException(error);
+        }
 
         return new Project(projectFile, version);
     }
@@ -25,33 +30,37 @@ public static bool IsVersionable(string projectFile)
     {
         try
         {
-            ReadVersion(projectFile);
-            return true;
+            var (success, _, _) = ReadVersion(projectFile);
+            return success;
         }
         catch (Exception)
         {
             return false;
         }
     }
 
-    private static SemanticVersion ReadVersion(string projectFile)
+    private static (bool, SemanticVersion, string) ReadVersion(string projectFile)
     {
         var doc =  ReadProject(projectFile);
 
         var versionString = SelectVersionNode(doc)?.InnerText;
 
         if (string.IsNullOrWhiteSpace(versionString))
         {
-            throw new InvalidOperationException($"Project {projectFile} contains no or an empty <Version> XML Element. Please add one if you want to version this project - for example use <Version>1.0.0</Version>");
+            return (false, 
+                null, 
+                $"Project {projectFile} contains no or an empty <Version> XML Element. Please add one if you want to version this project - for example use <Version>1.0.0</Version>"
+                );
         }
 
         try
         {
-            return SemanticVersion.Parse(versionString);
+            return (true, SemanticVersion.Parse(versionString),null);
         }
         catch (Exception)
         {
-            throw new InvalidOperationException($"Project {projectFile} contains an invalid version {versionString}. Please fix the currently contained version - for example use <Version>1.0.0</Version>");
+            return (false, null,
+            $"Project {projectFile} contains an invalid version {versionString}. Please fix the currently contained version - for example use <Version>1.0.0</Version>");
         }
     }