ln -t: a renamed target directory redirects the remaining links #15523

With a target directory (-t, or several sources), uutils ln checks once that the target is a directory and then creates each link, and renames each backup, by joining the directory's path. If that path is renamed or replaced while ln runs, the remaining links go wherever it leads now. GNU ln keeps them in the directory it started with.

An -i prompt makes the gap easy to hit:

$ mkdir dir other; touch a b c dir/a dir/b other/b
$ ln -s -i -t dir a b c
ln: replace 'dir/a'?

While it waits, run mv dir moved; ln -s other dir in another shell, then answer y to both prompts.

GNU coreutils 9.12 creates all three links in moved, and other/b is untouched.

uutils main creates them in other, replacing other/b.