common.ps1 uses .NET Core-only TrimEndingDirectorySeparator, breaking SPECIFY_INIT_DIR on Windows PowerShell 5.1

[kurtvalcorza]

Summary

scripts/powershell/common.ps1 resolves the project root with a .NET Core-only API, which is unavailable on Windows PowerShell 5.1 (.NET Framework). When SPECIFY_INIT_DIR is set, root resolution throws before any Spec Kit command can run.

The same file already documents this exact incompatibility — and then avoids it correctly 150 lines later.

The inconsistency

scripts/powershell/common.ps1:60:

$initRoot = [System.IO.Path]::TrimEndingDirectorySeparator($resolved.Path)

scripts/powershell/common.ps1:212-214:

# TrimEnd (not [Path]::TrimEndingDirectorySeparator, which is .NET Core
# only) keeps this working on Windows PowerShell 5.1 / .NET Framework.
$featureDirTrimmed = $featureDir.TrimEnd('/', '\')

So the codebase already knows TrimEndingDirectorySeparator is .NET Core only, and line 60 uses it anyway.

Impact

Windows PowerShell 5.1 users who set SPECIFY_INIT_DIR hit a Method invocation failed error during project-root resolution, before the requested command executes. Users on PowerShell 7+ are unaffected, which is likely why this hasn't surfaced widely.

Suggested fix

Use the same normalization the file already endorses:

$initRoot = $resolved.Path.TrimEnd('/', '\')

The stated no-op semantics still hold: TrimEnd is a no-op on a path with no trailing separator. Note it differs on a bare drive root (C:\ → C:), which is the one case worth a guard if that path is reachable here.

Version

Reproduced on main @ c0fe0e4 (v0.14.2).

Found by an automated review pass over a vendored copy in a downstream project; verified against upstream main before filing.