I use Git, SourceTree and Xcode on a Mac Lion machine. But I think I need an 'External Diff' tool. I will also most certainly need a Merge tool as well.
What is Meld?
Meld is a visual diff and merge tool targeted at developers. Meld helps you compare files, directories, and version controlled projects. It provides two- and three-way comparison of both files and directories, and has support for many popular version control systems.
Git Merge Tool Mac
Meld helps you review code changes and understand patches. It might even help you to figure out what is going on in that merge you keep avoiding.
Features

- I use Git, SourceTree and Xcode on a Mac Lion machine. But I think I need an 'External Diff' tool. I will also most certainly need a Merge tool as well.
- Today I asked myself: how to use an external Diff/Merge tool in Sourcetree? When you open the options of Sourcetree you will find the section for defining an external tool deactivated like this: As external tools are defined for Git and not for Sourcetree you have to allow Sourcetree itself to modify the.gitconfig file to use an external editor.
- Two- and three-way comparison of files and directories
- File comparisons update as you type
- Auto-merge mode and actions on change blocks help make merges easier
- Visualisations make it easier to compare your files
- Supports Git, Bazaar, Mercurial, Subversion, etc.
- …and more
Meld is licensed under the GPL v2, except as noted.
Getting it
Meld is packaged for most Linux/Unix distributions, including Fedora, Ubuntu, and Suse. Unless you want the absolutely latest version, you should install Meld through your package manager.
Windows users should download the MSI, or for older releases, check out the Meld installer project.
On OS X, Meld is not yet officially supported. For pre-built binaries, these OS X builds are the best option. You can also get Meld from MacPorts, Fink or Brew; none of these methods are supported.
You can also run Meld without installing it. Just extract the archive and run bin/meld from the archive folder.

| Source: | Meld 3.20.1 | 31 March 2019 |
| Windows: | Meld 3.20.0 | 6 January 2019 |
| Note: The 3.20 Windows build uses a new build chain. If you experience issues, please use Meld 3.18.3. | ||
Requirements
Mac Merg Tool For Source Tree Download

- Python 3.3
- GTK+ 3.14
- GLib 2.36
- PyGObject 3.14
- GtkSourceView 3.14
- pycairo