[tahoe-dev] down with filesystems! up with the web! -- Re: [tahoe-lafs] #776: users are confused by "tahoe rm"

[James A. Donald]

David-Sarah Hopwood wrote:
> All common operating systems [*] do allow symlinks to
> directories, which introduce all the same potential usability problems
> as hardlinks to directories, and more.
> 
> I'm more inclined to believe that disallowing hardlinks to directories
> was almost entirely a matter of implementation expedience: if links
> can form cycles, that implies either implementing GC or accepting leaks,
> and it is easier to disallow hardlinks to directories than to implement
> cycle prevention. Note that this theory is consistent with the HFS
> exception: Apple found a good enough reason to support acyclic hardlinks
> to directories, to justify the effort of implementing cycle prevention.

Acyclic directed graphs with bidirectional asymmetric links have many of 
the same advantages in ease of manipulation as trees with with 
bidirectional asymmetric links.  However, ensuring a graph remains 
acyclic under manipulation is trickier than ensuring a tree remains 
acyclic under manipulation, and is likely to become considerably 
trickier in a distributed system composed of unreliable elements.