Update the source file list of CMakeLists.txt under one directory.

script.ps1

$ErrorActionPreference = 'Stop'

function Get-SourceFiles ([String]$Dir) {
    Push-Location $Dir
    try {
        Get-ChildItem . -File -Recurse | Where-Object { $_.Extension -match '^\.(c|cpp|h|hpp)$' } | Resolve-Path -Relative | ForEach-Object { $_.TrimStart('.\').Replace('\', '/') } | Sort-Object
    }
    finally {
        Pop-Location
    }
}

function Update-SourceFileList {
    param (
        [Parameter(ValueFromPipeline)]
        [String]$Line,
        [String]$Dir = $PWD
    )
    begin {
        $take = $true
    }
    process {
        if ($take) {
            $Line
            $take = $Line -ne 'set(SOURCES'
        }
        elseif ($Line -eq ')') {
            Get-SourceFiles $Dir | ForEach-Object { "    $_" }
            ')'
            $take = $true
        }
    }
}

function Update-CMakeLists ([String]$Dir) {
    $file = Join-Path $Dir -ChildPath 'CMakeLists.txt' -Resolve
    $content = Get-Content $file | Update-SourceFileList -Dir $Dir
    Set-Content $file -Value $content
}