CustomPackageInstallationProcessor.cs

using Sitecore.Install.Framework;
using Sitecore.Diagnostics;
using Sitecore.IO;
using System.Linq;

public class CustomPackageInstallationProcessor : IItemInstallerEvents
{
    public void OnItemInstalling(object sender, InstallerEventArgs args)
    {
        Assert.ArgumentNotNull(sender, nameof(sender));
        Assert.ArgumentNotNull(args, nameof(args));

        var installationContext = args.InstallArgs.InstallationContext;
        var packageItems = installationContext.Items;

        foreach (var item in packageItems)
        {
            // Custom logic to decide if a file should be installed
            if (ShouldSkipItem(item))
            {
                Log.Info($"Skipping installation of item: {item.Name}", this);
                installationContext.Items.Remove(item);
            }
        }
    }

    private bool ShouldSkipItem(InstallerItem item)
    {
        // Define your criteria for skipping files here
        // For example, skip files based on file extension or name pattern
        var skipExtensions = new[] { ".config", ".txt" };
        var fileName = FileUtil.GetFileName(item.Name);

        return skipExtensions.Any(ext => fileName.EndsWith(ext, System.StringComparison.OrdinalIgnoreCase));
    }

    // Other interface methods (OnItemInstalled, OnItemUninstalling, etc.) can be left empty or implemented as needed
    public void OnItemInstalled(object sender, InstallerEventArgs args) { }
    public void OnItemUninstalling(object sender, InstallerEventArgs args) { }
    public void OnItemUninstalled(object sender, InstallerEventArgs args) { }
}