feat: Keep the root output directory in DocumentSet.Save()

Instead of deleteing the output directory recursively in DocumentSet.Save(), delete all child directories and
files, but keep the root output directory as it would be recreated afterwards anyways.

Closes #12

Author: ap0llo

src/MarkdownGenerator/Extensions/_Admonition/MdAdmonition.cs

@@ -7,7 +7,7 @@ namespace Grynwald.MarkdownGenerator.Extensions
     /// <summary>
     /// Represents a "admonition" in a markdown document implemented by
     /// the "Admonition" extension for Python-Markdown.
-    /// For details https://python-markdown.github.io/extensions/admonition/
+    /// For details see https://python-markdown.github.io/extensions/admonition/
     /// </summary>
     /// <remarks>
     /// Using this element will produce markdown which will not be rendered correctly

src/MarkdownGenerator/_Model/DocumentSet.cs

@@ -198,9 +198,22 @@ public void Save(string directoryPath, bool cleanOutputDirectory, Action<T, stri
             if (directoryPath == null)
                 throw new ArgumentNullException(nameof(directoryPath));
 
+            // If selected, delete all files and directories in the output directory
+            // Keep the root output directory unchanged (it would be recreated
+            // directly afterwards anyways). By keeping the directory
+            // we won't run into problems when an application still
+            // has the directory open.
             if (Directory.Exists(directoryPath) && cleanOutputDirectory)
             {
-                Directory.Delete(directoryPath, recursive: true);
+                foreach(var childDir in Directory.GetDirectories(directoryPath))
+                {
+                    Directory.Delete(childDir, recursive: true);
+                }
+
+                foreach(var file in Directory.GetFiles(directoryPath))
+                {
+                    File.Delete(file);
+                }
             }
 
             foreach (var keyValuePair in m_DocumentsByPath)