Better gulp tab expansion script

gulp-tab.ps1

# Copyright (c) 2014 Jason Jarrett
#
# Tab completion for the `gulp`
#
# Usage:
#
# To enable powershell <tab> completion for gulp you need to be running 
# at least PowerShell v3 or greater and add the below to your $PROFILE
#
#     Invoke-Expression ((gulp --completion=powershell) -join [System.Environment]::NewLine)
#     iex (iwr https://gist.githubusercontent.com/fearthecowboy/b832488906fe7cd99c422d8dea197618/raw/08bc0cdea834bc341f2986982aa74762c35e534f/gulp-tab.ps1)

# walks up to find the gulpfile (and supports extensions other than .js)
function Get-GulpFilePath($startPath) {
    $r = resolve-path "$startPath/gulpfile.*" 
    if ($r) {
        return $r[0]
    }
    $newPath = resolve-path -ea 0 "$startPath/../" -ErrorVariable x
    if( $newPath.Path -eq $startPath ) {
        return;
    }
    return Get-GulpFilePath($newPath)
}

$gulp_completion_Process = {
    param($commandName, $parameterName, $wordToComplete, $commandAst, $fakeBoundParameter)

	# Load up an assembly to read the gulpfile's sha1
	if(-not $global:GulpSHA1Managed) {
		[Reflection.Assembly]::LoadWithPartialName("System.Security") | out-null
		$global:GulpSHA1Managed = new-Object System.Security.Cryptography.SHA1Managed
	}

	# setup a global (in-memory) cache
	if(-not $global:GulpfileShaCache) {
		$global:GulpfileShaCache = @{};
	}

	$cache = $global:GulpfileShaCache;

	# Get the gulpfile's sha1
	$sha1gulpFile = ((Get-GulpFilePath .) | %{
		$file = [System.IO.File]::Open($_.Path, "open", "read")
		[string]::join('', ($global:GulpSHA1Managed.ComputeHash($file) | %{ $_.ToString("x2") }))
		$file.Dispose()
	})

    if ($sha1gulpFile) {
        # lookup the sha1 for previously cached task lists.
        if($cache.ContainsKey($sha1gulpFile)){
            $tasks = $cache[$sha1gulpFile];
        } else {
            $tasks = (gulp --tasks-simple).split("`n");
            $cache[$sha1gulpFile] = $tasks;
        }

        $tasks |
            where { $_.startswith($commandName) }
            Sort-Object |
            foreach { New-Object System.Management.Automation.CompletionResult $_, $_, 'ParameterValue', ('{0}' -f $_) }
    }
}

if (-not $global:options) {
    $global:options = @{
        CustomArgumentCompleters = @{};
        NativeArgumentCompleters = @{}
    }
}

$global:options['NativeArgumentCompleters']['gulp'] = $gulp_completion_Process
$function:tabexpansion2 = $function:tabexpansion2 -replace 'End\r\n{','End { if ($null -ne $options) { $options += $global:options} else {$options = $global:options}'