Work around .NET Core execute permission behavior

Author: bording

LibGit2Sharp.Tests/TestHelpers/BaseFixture.cs

@@ -383,10 +383,18 @@ protected static string Touch(string parent, string file, string content = null,
             string dir = Path.GetDirectoryName(filePath);
             Debug.Assert(dir != null);
 
+            var newFile = !File.Exists(filePath);
+
             Directory.CreateDirectory(dir);
 
             File.WriteAllText(filePath, content ?? string.Empty, encoding ?? Encoding.ASCII);
 
+            //Work around .NET Core 1.x behavior where all newly created files have execute permissions set.
+            if (Constants.IsRunningOnUnix && newFile)
+            {
+                RemoveExecutePermissions(filePath, newFile);
+            }
+
             return filePath;
         }
 
@@ -398,6 +406,8 @@ protected static string Touch(string parent, string file, Stream stream)
             string dir = Path.GetDirectoryName(filePath);
             Debug.Assert(dir != null);
 
+            var newFile = !File.Exists(filePath);
+
             Directory.CreateDirectory(dir);
 
             using (var fs = File.Open(filePath, FileMode.Create))
@@ -406,9 +416,21 @@ protected static string Touch(string parent, string file, Stream stream)
                 fs.Flush();
             }
 
+            //Work around .NET Core 1.x behavior where all newly created files have execute permissions set.
+            if (Constants.IsRunningOnUnix && newFile)
+            {
+                RemoveExecutePermissions(filePath, newFile);
+            }
+
             return filePath;
         }
 
+        private static void RemoveExecutePermissions(string filePath, bool newFile)
+        {
+            var process = Process.Start("chmod", $"644 {filePath}");
+            process.WaitForExit();
+        }
+
         protected string Expected(string filename)
         {
             return File.ReadAllText(Path.Combine(ResourcesDirectory.FullName, "expected/" + filename));