Sometimes you need to diff two branches, and your source control system isn’t the right tool for the job. I’ve ran into this problem in practice in a few different cases:

• Merging from one source control system to a different one
• GitHub sometimes fails at this task

Whatever the reason for needing to do this, the same general solution can be applied: diff the folders using WinMerge. In this article I’ll be showing you how to use WinMerge to do this task.

1 – Example – Old Branch and New Branch

Here’s a simple example of two branches – named Old Branch and New Branch.

Old Branch

New Branch

In the new branch I made the following changes:

1. Program.cs – extracted out the StoreRepository class to its own file
2. StoreRepository.cs – added this new file
3. Store.cs – removed unused references

2 – Install WinMerge

1. Go to https://winmerge.org/downloads/?lang=en
2. Download and install the version that’s right for you

3 – Select the Old Branch and New Branch to diff them

• Left=Old Branch
• Right=New Branch
• Make sure to check Include Subfolders.

4 – Analyze the diffs

Hide the ones with no changes

If you’re dealing with a large number of files, it helps to hide the files with no changes.

1. Right-click all the files with “Text files are identical”
2. Click Hide Items

   

View the diffs and merge them

1. Right-click the file -> Compare

   

2. Use hotkeys to select the diff and copy it to the right
   • Alt-Down = select the next diff
   • Alt-Right = copy the changes from the left to the right

     

3. Because the files are now the same, it’ll show this prompt. Click OK.

   

4. Ctrl-S to save the merged file

View the new files

1. Right-click the file that says “Right only:…”
2. Click Open Right -> with External Editor

   

This will open the file in Notepad. You can verify the file is what you expected, or make edits if there’s any changes needed.