Translating PSDrive-based path arguments for external (native) executables is overzealous (PSNativePSPathResolution)

PR #12386 introduced experimental feature PSNativePSPathResolution, which as of (at least) PowerShell Core 7.1.0-preview.7 has become a default feature.

• For problems with this feature in general, see #13644

Its purpose is to translate PowerShell-drive-based paths to native filesystem paths, because external executables only understand the latter.

This translation is currently overzealous in that it nonsensically translates an argument that starts with : (which clearly isn’t a drive-based path).

@DHowett has pinpointed the problematic behavior to: https://github.com/PowerShell/PowerShell/blob/3effa204103460c996a8612aa70718fdf924047d/src/System.Management.Automation/engine/NativeCommandParameterBinder.cs#L388-L406

Steps to reproduce

On Unix:

/bin/echo :foo | Should -Be ':foo'

On Windows:

cmd /c echo :foo | Should -Be ':foo'

Expected behavior

The test should succeed.

Actual behavior

The test fails, because the the current location’s path is unexpectedly prepended to :

Expected strings to be the same, but they were different. Expected length: 4 Actual length:   44 Strings differ at index 0.
Expected: ':foo' But was:  '/Users/jdoe...'

Environment data

PowerShell Core 7.1.0-preview.7

[DHowett]

I do not believe that Issue-Question is the appropriate label for this issue. This is a significant regression in native tool use from one preview release to another, and we are at risk of shipping with it.

[SteveL-MSFT]

For 7.1, I’m going to revert the change to make this non-experimental