The "Locked" file attribute is a Mac-only setting you can set or reset in the Finder (using the get-info command on the file/directory). It is NOT making the file/directory "ReadOnly". It only prevents the user from dragging the item to the trash, and empty the trash. When set for a directory, it has no effect on the contents (files and directories) within that directory.

I use it on the repository directory, to ensure I don't delete it by mistake. All development tools (and Git!) work fine on this repository.

However - if I try to resolve a merge conflict using external merge tool (no matter what tool is chosen in the preferences) it fails - because git fails to create the _LOCAL, _REMOTE, _BASE versions of the conflicted file. They simply are not created.

This is NOT a "readonly" problem, because git DOES create the .orig and _BACKUP versions of that same file.

Of course the external merge tool, when launched, fails to find the files to merge, and fails.

Resetting the "Locked" attribute on the repository removes the problem.

This is not strictly a SourceTree problem, because using the "git mergetool" command from the terminal yields similar results. However, SourceTree comes with git embedded, and it might be in your interest to resolve the issue.

This is a NEW issue, as I worked fine before with the "Locked" flag set for my repositories, but I can't tell WHEN the problem started.