Support package trees containing absolute symlinks about stow

[z1atk0]

Hi!

Strangely enough, I only experienced this issue starting with 2.4.0. Up to & including 2.3.1, both stowing and unstowing of absolute symlinks has never been a problem before (and I've been using stow since the early 1.3.x days, almost as long as I've been using Linux itself), despite the comment in https://github.com/aspiers/stow/blob/master/lib/Stow.pm.in#L503 (which I never knew about, as it just worked as expected all those years 🤷‍♂️).

I have not unrolled the whole history of this issue yet, but I don't understand what would actually be the problem with stowing and unstowing an absolute symlink. As far as I understand, unstowing means the deletion of relative symlinks. What difference does it make where this relative symlink is pointing to (I understand of course the difference between pointing to a directory vs. pointing to a file with regards to folding/unfolding, but why is it any different depending on what file type the symlink points to?

To break it down, manually doing ...

ln -s ../stow/some_package/bin/actual_file /usr/local/bin/actual_file
ln -s ../stow/some_package/share/doc/package/absolute_symlink_to_somewhere /usr/local/share/doc/package/absolute_symlink_to_somewhere
ln -s ../stow/some_package/dev/package_device_node /usr/local/dev/package_device_node
ln -s ../stow/some/package/var/run/package_socket /usr/local/var/run/package_socket

... would work just fine, as would ...

rm /usr/local/bin/actual_file
rm /usr/local/share/doc/package/absolute_symlink_to_somewhere
rm /usr/local/dev/package_device_node
rm /usr/local/var/run/package_socket

... to remove the symlinks again, without breaking anything. So what is the reason for the strange special-casing of absolute symlinks? Does it have to do with stow's complex folding/unfolding logic (which I admittedly didn't consider at all here 😇)? Are there some tricky non-obvious corner cases that I'm missing here?

And, if this change in behaviour from 2.3.1 to 2.4.0 was intentional, could you please point me to the commit that is responsible for it, so that I can keep a local diff around to revert it back to the old behaviour? 🤓

Thanks for listening! 🙂