FileMerge quits immediately after launching from SourceTree

Question

I regularly use Atlassian SourceTree (on Mac OS X) to launch FileMerge to resolve git merge conflicts. Out of the blue it has stopped working: when I right click and select

Answer 1

This helped: https://gist.github.com/kylefox/4512777

Tell system when 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