You will need git and visual studio 2019 (visual studio 2019 community works fine)
With all these changes mod assistant will install the bsipa from _local_mods\bspia.zip
If you want a specific version of mod assistant or bsipa you will need to checkout that
specifc version after cloning it (cd into the folder and: git checkout <commit id> --force)


getting latest mod assistant:
git clone https://github.com/Assistant/ModAssistant.git

getting latest bsipa
git clone https://github.com/beat-saber-modding-group/BeatSaber-IPA-Reloaded.git --recursive


File BeatSaber-IPA-Reloaded\bsinstalldir.txt
Must contain the path to the game (I usually compile on a different computer, the path can be
different, it might be that the version of the game has to be the same) with regular slashes,
ending with a slash, without new lines, encoded in UTF8 without BOM(use notepad/notepad++)
example:
G:/games/Beat Saber/


File BeatSaber-IPA-Reloaded\IPA.Injector\AntiPiracy.cs
from:
        public static bool IsInvalid(string path)
        {
to:
        public static bool IsInvalid(string path)
        {
            return false;


File BeatSaber-IPA-Reloaded\IPA.Loader\Config\SelfConfig.cs
from:
public virtual bool Regenerate { get; set; } = true;
to:
public virtual bool Regenerate { get; set; } = false;

from:
            public virtual bool AutoUpdate { get; set; } = true;
to:
            public virtual bool AutoUpdate { get; set; } = false;

from:
            public virtual bool AutoCheckUpdates { get; set; } = true;
to:
            public virtual bool AutoCheckUpdates { get; set; } = false;


File ModAssistant\ModAssistant\Classes\Updater.cs
from:
        public static async Task<bool> CheckForUpdate()
        {
to:
        public static async Task<bool> CheckForUpdate()
        {
            return false;


File ModAssistant\ModAssistant\Classes\Utils.cs
from:
        public static bool IsVoid()
        {
to:
        public static bool IsVoid()
        {
            return false;


File ModAssistant\ModAssistant\Pages\Mods.xaml\Mods.xaml.cs
This file contains the changes that make mod assistant install bsipa from _local_mods
from:
                if (mod.name.ToLowerInvariant() == "bsipa")
                {
                    MainWindow.Instance.MainText = $"{string.Format((string)FindResource("Mods:InstallingMod"), mod.name)}...";
                    await Task.Run(async () => await InstallMod(mod, installDirectory));
to:
                if (mod.name.ToLowerInvariant() == "bsipa")
                {
                    MainWindow.Instance.MainText = $"{string.Format((string)FindResource("Mods:InstallingMod"), mod.name)}...";
                    await Task.Run(async () => await InstallModLocal(mod, installDirectory));

from:
        private async Task InstallMod(Mod mod, string directory)
to:
        private async Task InstallModLocal(Mod mod, string directory)
        {
            string installDirectory = App.BeatSaberInstallDirectory;
            string localDir = Path.Combine(installDirectory, "_local_mods");
            string localZip = Path.Combine(localDir, $"{mod.name.ToLower()}.zip");

            if (!Directory.Exists(localDir) || !File.Exists(localZip))
            {
                System.Windows.MessageBox.Show(string.Format((string)FindResource("Mods:ModDownloadLinkMissing"), mod.name));
                return;
            }

            using (FileStream zipToOpen = new FileStream(localZip, FileMode.Open))
            {
                using (ZipArchive archive = new ZipArchive(zipToOpen, ZipArchiveMode.Update))
                {
                    foreach (ZipArchiveEntry file in archive.Entries)
                    {
                        string fileDirectory = Path.GetDirectoryName(Path.Combine(directory, file.FullName));
                        if (!Directory.Exists(fileDirectory))
                        {
                            Directory.CreateDirectory(fileDirectory);
                        }

                        if (!String.IsNullOrEmpty(file.Name))
                        {
                            await ExtractFile(file, Path.Combine(directory, file.FullName), 3.0, mod.name, 10);
                        }
                    }
                }
            }
        }
        private async Task InstallMod(Mod mod, string directory)


for bsipa:
save changes made
build->configuration manager: release, x64, close
build->clean solution
build->rebuild solution
compress files from BSIPA-Meta\bin\x64\Release\Net461 to <game dir>\_local_mods\bsipa.zip

for mod assistant:
save changes made
build->configuration manager: release, close
build->clean solution
build->rebuild solution
copy ModAssistant.exe from ModAssistant\bin\Release to <game dir>