When working on a project, either an open-source project where several people review your code, or a commercial project where you sell a component with your source code, there will be people and customers who find bugs or want to improve your project. To do that they send you patches which you have to review and decide if you want to apply them.
TortoiseGitMerge helps you with both those tasks:
Applying the patches
TortoiseGitMerge also helps you to sort out conflicted files which can occur if you're working with a source control system and others are working on the same files as you.
TortoiseGitMerge is free. You don't have to pay for it, you can use it any way you want. It is developed under the GP license (GPL).
TortoiseGitMerge is an Open Source project. That means you have full read access to the source code of this program. You can browse it on this link https://tortoisegit.org/sourcecode .