Adding to .zip archive removes file system access rules

Start in src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs at the finalization code around lines 3132-3143 and the temporary and final output handling around lines 4663-4713. Reproduce the issue with the supplied AddEntryRevertingFilePermissions test, then add regression coverage showing that an access rule on the archive remains after CommitUpdate().

When adding to a .zip archive on disk, the update does not happen in place. Instead, a temporary .zip file with the updated contents is created in a temporary directory first, which replaces the original archive after a successful write. As a result, any file system access rules set on the .zip archive that is updated are lost.

Steps to reproduce

1. Run the snippet below in a debugger

		[Test]
		[Category("Zip")]
		[Category("CreatesTempFile")]
		public void AddEntryRevertingFilePermissions()
		{
			const string TestValue = "0001000";
			string tempFile = "c:/temp/";
			Assert.IsNotNull(tempFile, "No permission to execute this test?");

			tempFile = Path.Combine(tempFile, "SharpZipTest.Zip");

			// create empty zip file
			using (ZipFile f = ZipFile.Create(tempFile))
			{
				f.BeginUpdate();
				f.CommitUpdate();
			}

			Console.WriteLine("break here and manually amend permissions for c:/temp/SharpZipTest.Zip by adding a rule");

			using (ZipFile f = new ZipFile(tempFile))
			{
				var m = new StringMemoryDataSource(TestValue);
				f.BeginUpdate();
				f.Add(m, "a.dat");
				f.CommitUpdate();
			}

			Console.WriteLine("permissions for c:/temp/SharpZipTest.Zip are reverted");
		}

2. Break in the middle and amend permissions to the file by adding an access rule.
3. Run to completion and verify that the file permission has reverted.

Expected behavior

File permissions should be retained

Actual behavior

File permissions inherited from temporary directory (e.g. C:\Users\username\AppData\Local\Temp\) are set

Version of SharpZipLib

Obtained from (only keep the relevant lines)

• Compiled from source, commit: https://github.com/icsharpcode/SharpZipLib/commit/cd5310f5b7eed595110b76a2f7ae5ee013cc50f1

Further detail

The update is finalised: (directUpdate is false)
https://github.com/icsharpcode/SharpZipLib/blob/cd5310f5b7eed595110b76a2f7ae5ee013cc50f1/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs#L3132-L3143

The temporary output (pointing to a temporary directory ) is created at https://github.com/icsharpcode/SharpZipLib/blob/cd5310f5b7eed595110b76a2f7ae5ee013cc50f1/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs#L4663-L4669

The final output is created at
https://github.com/icsharpcode/SharpZipLib/blob/cd5310f5b7eed595110b76a2f7ae5ee013cc50f1/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs#L4676-L4713