ln -sfn is not atomic

[dimo414]

According to this post ln -sfn isn't actually atomic, despite the comment here. Need to confirm this is actually broken and then fix, presumably to the rename approach described in the post.

[dimo414]

bkt uses the rename pattern, for reference.

[devkev]

A recent comment on the same answer claims that the ln in modern coreutils does the atomic rename approach now.