Directory traversal/output bugs in DosBatchRoutingIntegrationTests

[assumenothing]

Describe the bug
There are several tests in the class DosBatchRoutingIntegrationTests which test for the output files in the wrong directories.

1. HostRequestedBatch_Cd_ChangesDirectory_ThenPrintsNew() - The batch file should write "OUT.TXT" into DOS-mapped folder "C:\SUBDIR\OUT.TXT". Test currently assumes root of drive.
2. HostRequestedBatch_CdDot_StaysInCurrentDirectory() - The batch file should write "OUT.TXT" into DOS-mapped folder "C:\SUB\OUT.TXT". Test currently assumes root of drive.
3. HostRequestedBatch_Md_CreatesDirectory() - The batch file should write "OUT.TXT" into DOS-mapped folder "C:\NEWDIR\OUT.TXT". Test currently assumes root of drive.
4. HostRequestedBatch_Mkdir_IsAliasForMd() - The batch file should write "OUT.TXT" into DOS-mapped folder "C:\SUBDIR\OUT.TXT". Test currently assumes root of drive.

To Reproduce
Run unit tests for "DosBatchRoutingIntegrationTests". The tests should fail in their current form.

Expected behavior
The tests should not be passing in their current form. If the unit tests are currently passing, then there are likely problems with the way that file paths are being resolved in the batch files or other DOS filesystem APIs.

Test system

• OS: Windows 11 version 25H2
• .NET 10 Installed Runtimes: Microsoft.AspNetCore.App 10.0.7, Microsoft.NETCore.App 10.0.7, Microsoft.WindowsDesktop.App 10.0.7
• .NET 10 Installed SDK Version: 10.0.203

Additional context
I found this while experimenting with changes to various internal file system and drive-related APIs. I had patched a number of methods inside DosPathResolver, including a full rewrite of the GetFullDosPathIncludingRoot method--which you currently are using a bad path traversal algorithm.

I likely found/fixed the bug while I was messing around with rewriting DosDriveManager. Though at the time when I made these local source changes (this last weekend), I didn't realize that there is currently heavy development inside those APIs right now.

There are currently two possible fixes that I can see for these tests to be correct:

1. Modify the batch scripts in the tests to use > \OUT.TXT so "OUT.TXT" is always located at the root of the current drive specified.
2. Modify the tests so they reference the proper directories where "OUT.TXT" is being written (by adding the required sub-directories to the Path.Join calls.

[maximilien-noal]

Hi,

Thanks for finding this issue and taking the time to describe it so clearly.

Yes there is a very large PR for floppy emulation, floppy images, and MSCDEX support, and it touches BAT file support a bit and possibly filepath resolution, but it may not work out in the end. I think in its current form it's too large to be reviewed, and I don't think it touches the DosPathResolver.

Anyway, don't let it block you from sending a PR. The current heavy work by Copilot is only a draft experiment.