Fix shadow copy up to date check on startup

[BrennanConroy]

Fixes #48233

If using shadow copy in ANCM and you shutdown the app (e.g. app_offline.htm) then delete a subfolder (with a dll), starting up the app can cause a crash that can only be resolved by adding back the deleted folder. Or resolved by deleting the shadow copy folder (either manually or with cleanShadowCopyDirectory setting turned on).

The issue submitter helpfully pointed out the code that was problematic, we basically swapped which directory is the "main" directory every recursion of the up to date function. The fix is simple, keep the app directory as the main directory.

Test added that repros the scenario.

[amcasey]

Kudos, @someguy20336!

[antmjones]

Is there any possibility of this fix being included in a 8.0.x point release? I was caught out by this today and it was far from immediately obvious what had gone wrong (thanks again to @someguy20336 for the detailed info in the original report!)

I now know there's a workaround with setting cleanShadowCopyDirectory to true, but presumably this is going to have an impact on application startup time (given it will prevent skipping copying of files where the last write time is unchanged - https://github.com/dotnet/dotnet/blob/v8.0.4/src/aspnetcore/src/Servers/IIS/AspNetCoreModuleV2/CommonLib/Environment.cpp#L187).

[BrennanConroy]

/backport to release/8.0

[github-actions]

Started backporting to release/8.0: https://github.com/dotnet/aspnetcore/actions/runs/9025051117

[github-actions]

@BrennanConroy backporting to release/8.0 failed, the patch most likely resulted in conflicts:

$ git am --3way --ignore-whitespace --keep-non-patch changes.patch

Applying: Fix shadow copy up to date check on startup
Using index info to reconstruct a base tree...
M	src/Servers/IIS/IIS/test/IIS.ShadowCopy.Tests/ShadowCopyTests.cs
Falling back to patching base and 3-way merge...
Auto-merging src/Servers/IIS/IIS/test/IIS.ShadowCopy.Tests/ShadowCopyTests.cs
CONFLICT (content): Merge conflict in src/Servers/IIS/IIS/test/IIS.ShadowCopy.Tests/ShadowCopyTests.cs
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Fix shadow copy up to date check on startup
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

[github-actions]

@BrennanConroy an error occurred while backporting to release/8.0, please check the run log for details!

Error: git am failed, most likely due to a merge conflict.