Hi,
Just to let you know: I've found that the entry excludesfile in .gitconfig was erased (after seeing some mess in a commit).
It seems that in SourceTree, if you touch some option without setting the "Global ignore list" in the Git tab (it comes empty by default) , it will overwrite the excludesfile you had in .gitconfig.
No problem now that it's updated but may be annoying.
Regards,