Better SourceTree with Mono.Cecil

Introduction

I am using Git for a while, but I hate git console for Windows. But some time ago Scott Hanselman published how to integrate Git with PowerShell which is exactly what I need. Instead of old cmd I have all features from PowerShell.

Sometime ago my friends show me SourceTree, which is quite nice tool. But it has a one irritating button: Terminal, which opens Git console or cmd. But I hate git console and I hate cmd, I would like to open PowerShell instead. I look all the options but I cannot find anyway to change this button action, or at least hide it.

What does this button do?

Because I didn’t find any useful option, I decided to check the source. But SourceTree is not open-source app, which is quite strange in this days ;)

SourceTree is .NET application, so we can restore “our” code using some dedicated tools like dotPeek or ILSpy. I find out that terminal button handler looks like following:

public void LaunchGitBashPrompt(string path)
{
  string str = GeneralHelper.CombinePath(RepoHandlerGit.GitBasePath(), "bin\\sh.exe");
  ProcessStartInfo startInfo = new ProcessStartInfo("cmd.exe");
  if (path != null)
    startInfo.WorkingDirectory = path;
  startInfo.Arguments = string.Format("/c \"{0}\" --login -i", (object) str);
  Process.Start(startInfo);
}

All the stings are hardcoded, so there isn’t an easy way to replace them.

Mono.Cecil to the rescue.

Quoting offical site (the most importat part is bolded):

Cecil is a library written by Jb Evain to generate and inspect programs and libraries in the ECMA CIL format. It has full support for generics, and support some debugging symbol format.

In simple English, with Cecil, you can load existing managed assemblies, browse all the contained types, modify them on the fly and save back to the disk the modified assembly.

Today it is used by the Mono Debugger, the bug-finding and compliance checking tool Gendarme, MoMA, DB4O, as well as many other tools.

So I produce simple Console application:

    public static void Main(string[] args)
    {
         const string powershellLink =
            @"C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessories\Windows PowerShell\Windows PowerShell.lnk";
        const string powershellArgs = " -NoExit \"cd '{0}';\"";

        var resolver = new DefaultAssemblyResolver();
        resolver.AddSearchDirectory(@"C:\tempSourceTree\sourceMy");

        var parameters = new ReaderParameters
        {
            AssemblyResolver = resolver,
        };

        var assembly = AssemblyDefinition.ReadAssembly(@"C:\tempSourceTree\sourceMy\SourceTree2.exe", parameters);

        var repoHandlerGit = assembly.MainModule.Types.First(x => x.Name.EndsWith("RepoHandlerGit"));
        Console.WriteLine(repoHandlerGit);
        var launchGitBashPrompt = repoHandlerGit.Methods.First(x => x.Name == "LaunchGitBashPrompt");
        Console.WriteLine(launchGitBashPrompt);

        var cmdString = launchGitBashPrompt.Body.Instructions.First(x => "cmd.exe".Equals(x.Operand));

        cmdString.Operand = powershellLink;

        var argsString = launchGitBashPrompt.Body.Instructions.First(x => x.Operand != null && x.Operand is string && ((string)x.Operand).Contains("login"));

        argsString.Operand = powershellArgs;

        launchGitBashPrompt.Body.Instructions[14] = launchGitBashPrompt.Body.Instructions[10];


        assembly.Write(@"C:\tempSourceTree\sourceMy\SourceTree.exe");
        Console.WriteLine("Done");
        Console.ReadLine();
    }

To use it copy SourceTree instalation into temp folder (in my case C:\tempSourceTree\sourceMy) and rename SourceTree.exe to SourceTree2.exe. After execution just replace SourceTree.exe with new file

That all folks.

p.s. I hoper bext time Atlassian will just show us code and I don’t have to use dirty tricks.