How to use XCode's mergetool to resolve conflicts?

Question

I'm in the middle of a rebase and I need to fix some merge conflicts. When I open the file in XCode, I see the source control conflict markers (<<<<<<<, etc) in the file.

How can I use XCode's mergetool to resolve these conflicts in a graphical fashion? I'm looking for this screen:

Answer 1

Pulling the answer from here

# Tell system where Xcode utilities live:
sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer

# Set "opendiff" as the default mergetool globally:
git config --global merge.tool opendiff

Then, when git tells you that there is a conflict, you can run git mergetool and it will open XCode's mergetool (like in the question's screenshot) and you can work through the conflict.

Answer 2

The FileMerge tool is a separate application, which you can open from the Xcode menu: