Refactor DirectoryHelper

Rename TryDeleteDirectory(string, int, int, int) to DeleteDirectory(...)
because this method can still throw exceptions and is not fully in line
with the try-parse pattern.

Introduce TryDeleteDirectory(string) : bool as a try-parse pattern-compliant
option to delete directories recursively without throwing exceptions.

Remove DeleteSubdirectories(string) method because it is not used anywhere.

Use 'var' keyword consistently across all methods.

Related to #980

Author: ThomasBarnekow

LibGit2Sharp.Tests/TestHelpers/DirectoryHelper.cs

@@ -15,15 +15,17 @@ public static class DirectoryHelper
             { "gitmodules", ".gitmodules" },
         };
 
+        private static readonly Type[] whitelist = { typeof(IOException), typeof(UnauthorizedAccessException) };
+
         public static void CopyFilesRecursively(DirectoryInfo source, DirectoryInfo target)
         {
             // From http://stackoverflow.com/questions/58744/best-way-to-copy-the-entire-contents-of-a-directory-in-c/58779#58779
 
-            foreach (DirectoryInfo dir in source.GetDirectories())
+            foreach (var dir in source.GetDirectories())
             {
                 CopyFilesRecursively(dir, target.CreateSubdirectory(Rename(dir.Name)));
             }
-            foreach (FileInfo file in source.GetFiles())
+            foreach (var file in source.GetFiles())
             {
                 file.CopyTo(Path.Combine(target.FullName, Rename(file.Name)));
             }
@@ -34,12 +36,16 @@ private static string Rename(string name)
             return toRename.ContainsKey(name) ? toRename[name] : name;
         }
 
-        public static void DeleteSubdirectories(string parentPath)
+        public static bool TryDeleteDirectory(string directoryPath)
         {
-            string[] dirs = Directory.GetDirectories(parentPath);
-            foreach (string dir in dirs)
+            try
+            {
+                DeleteDirectory(directoryPath);
+                return true;
+            }
+            catch (Exception)
             {
-                DeleteDirectory(dir);
+                return false;
             }
         }
 
@@ -53,30 +59,28 @@ public static void DeleteDirectory(string directoryPath)
                 return;
             }
             NormalizeAttributes(directoryPath);
-            TryDeleteDirectory(directoryPath, maxAttempts: 5, initialTimeout: 16, timeoutFactor: 2);
+            DeleteDirectory(directoryPath, maxAttempts: 5, initialTimeout: 16, timeoutFactor: 2);
         }
 
         private static void NormalizeAttributes(string directoryPath)
         {
-            string[] files = Directory.GetFiles(directoryPath);
-            string[] dirs = Directory.GetDirectories(directoryPath);
+            var files = Directory.GetFiles(directoryPath);
+            var dirs = Directory.GetDirectories(directoryPath);
 
-            foreach (string file in files)
+            foreach (var file in files)
             {
                 File.SetAttributes(file, FileAttributes.Normal);
             }
-            foreach (string dir in dirs)
+            foreach (var dir in dirs)
             {
                 NormalizeAttributes(dir);
             }
             File.SetAttributes(directoryPath, FileAttributes.Normal);
         }
 
-        private static readonly Type[] whitelist = { typeof(IOException), typeof(UnauthorizedAccessException) };
-
-        private static void TryDeleteDirectory(string directoryPath, int maxAttempts, int initialTimeout, int timeoutFactor)
+        private static void DeleteDirectory(string directoryPath, int maxAttempts, int initialTimeout, int timeoutFactor)
         {
-            for (int attempt = 1; attempt <= maxAttempts; attempt++)
+            for (var attempt = 1; attempt <= maxAttempts; attempt++)
             {
                 try
                 {