SetupBeyondCompareAsVSDiffTool.ps1

# .Synopsys
# Sets up Beyond Compare professional as Diff tool for all instances of Visual Studio on this PC
# If you don't use TFS, change the sccProvider as appropriate
[CmdLetBinding()]
param(
    $bcPath = 'C:\Program Files (x86)\Beyond Compare 3\BComp.exe',
    $sccProvider = 'TeamFoundation'
)

$ErrorActionPreference = 'stop';
$baseKey = 'REGISTRY::\HKCU\Software\Microsoft\VisualStudio\*'

function SetRegKeyProperties($keyPath, [hashtable]$keyProps){
    if(!(Test-Path $keyPath)){
        Write-Verbose "Creating $keyPath"
        # Force required here to recursively create registry path
        [void] (new-item $keyPath -Type:Directory -Force);
    }
    foreach($prop in $keyProps.GetEnumerator()){
        Set-ItemProperty -Path:$keyPath -Name:$prop.Key -Value:$prop.Value;
    }
}

$configBases = dir $baseKey | ? { $_.PSChildName -match '^\d+\.\d$' }
foreach($item in $configBases){
    Write-Host "Configuring $item"

    $diffToolsKey = Join-Path $item.PSPath "$sccProvider\SourceControl\DiffTools"
    SetRegKeyProperties (Join-path $diffToolsKey '.*\Compare') @{Command=$bcPath;Arguments='%1 %2 /title1=%6 /title2=%7'}
    SetRegKeyProperties (Join-path $diffToolsKey '.*\Merge') @{Command=$bcPath;Arguments='%1 %2 %3 %4 /title1=%6 /title2=%7 /title3=%8 /title4=%9'}
}

Change $bcPath to 'C:\Program Files\Beyond Compare 4\BComp.exe' if using Beyond Compare 4