yesterday I could merge files in sourcetree with the external tool filemerge. Today, sourcetree wanted me to register me, and after my successful registration, I couldnt start filemerge.
When I choose "Launch external diff tool" from the contextmenu of a file, 4 files appear (Backup, base, local and remote) but filemerge quits immediately.
When I launch external diff, filemerge displays in the left /dev/null as source. How can I fix it? In preferences I choose filemerge as external diff tool. Have I to write the diff command for source tree manually, to give it the right local version of my file? How can I do it?
Thanks
I had the same problem with SourceTree where I tried to use "open in external merge tool". The FileMerge app exited immediately.
I did not have the merge conflict in a file that had been deleted one place or another, but in a single file that just changed.
I could not find the root cause but could work around using the command line:
git mergetool
This opened FileMerge just fine and I could resolved the conflict in FileMerge, save, quit, back to SourceTree, refresh, and the conflict was resolved.
来源：https://stackoverflow.com/questions/16394718/sourcetree-filemerge-quits-immediately-and-creates-4-files-how-to-fix-it