Program.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace vscmd {
  class Program {
    static VisualStudio vs;

    [STAThread]
    static void Main(string[] args) {
      try {
        vs = VisualStudio.GetOrCreate();
        bool activate = false;
        for (var i = 0; i < args.Length; i++) {
          var arg = args[i];
          if ("args".StartsWith(arg)) {
            HandleDebugArguments(args.Skip(1));
          } else if ("attach".StartsWith(arg)) {
            HandleAttach(args.Skip(1));
          } else if ("start".StartsWith(arg)) {
            HandleDebugStart(args.Skip(1));
          } else {
            activate |= HandleFileArguments(args);
          }
          break;
        }
        if (activate)
          vs.ActivateMainWindow();
      } catch (Exception err) {
        Console.Error.WriteLine(err.ToString());
      }
    }

    static FileInfo[] GetFiles(string arg) {
      var directoryName = Path.GetDirectoryName(arg);
      var dir = new DirectoryInfo(string.IsNullOrEmpty(directoryName) ? Directory.GetCurrentDirectory() : directoryName);
      return dir.GetFiles(Path.GetFileName(arg));
    }

    static bool HandleFileArguments(IEnumerable<string> args) {
      bool handled = false;
      foreach (var arg in args) {
        if (arg.Contains('*') || arg.Contains('?')) {
          foreach (var file in GetFiles(arg)) {
            vs.OpenFile(file);
            handled = true;
          }
          continue;
        }

        vs.OpenFile(new FileInfo(arg));
        handled = true;
      }
      return handled;
    }

    static void HandleDebugStart(IEnumerable<string> args) {
      var config = vs.StartupProject.ActiveConfiguration;
      var program = args.FirstOrDefault();
      if (program == null) {
        Console.Out.WriteLine(config.DebugStartProgram);
        Console.Out.WriteLine(config.DebugStartArguments);
        return;
      }

      config.DebugStartProgram = Path.GetFullPath(program);

      args = args.Skip(1);
      if (args.Any())
        HandleDebugArguments(args);

      vs.Debugger.Go(false);
    }

    static void HandleDebugArguments(IEnumerable<string> args) {
      var config = vs.StartupProject.ActiveConfiguration;
      if (!args.Any()) {
        Console.Out.WriteLine(config.DebugStartArguments);
        return;
      }

      args = args.Select(arg =>
          QuoteIfNeeded(File.Exists(arg) ? Path.GetFullPath(arg) : arg));
      config.DebugStartArguments = string.Join(" ", args);
    }

    static void HandleAttach(IEnumerable<string> args) {
      var filters = args
          .Select<string, Func<Process, bool>>(s => {
            int id;
            if (int.TryParse(s, out id))
              return p => p.ProcessID == id;
            return p => p.Name.Contains(s);
          }).ToList();
      var debugger = vs.Debugger;
      if (!filters.Any()) {
        var processes = debugger.LocalProcesses
            .OrderBy(p => p.Name);
        foreach (var process in processes)
          Console.WriteLine($"{process.ProcessID,5} {process.Name}");
        return;
      }
      foreach (var process in debugger.LocalProcesses) {
        if (!filters.Any(f => f(process)))
          continue;
        Console.WriteLine($"{process.ProcessID,5} {process.Name}");
        process.Attach();
      }
    }

    static string QuoteIfNeeded(string arg) {
      if (!arg.Contains(' '))
        return arg;
      return string.Concat("\"", arg, "\"");
    }
  }
}