[tahoe-dev] notes about DIR2:CHK deep immutability (maybe Tahoe-LAFS v1.6)

[Brian Warner]

Zooko Wilcox-O'Hearn wrote:

> There could optionally be a command to deep-walk a directory graph  
> and produce an immutable snapshot of everything.

Kevin Reid wrote:

> Even if that isn't relevant, IMO there should be at least a utility
> which is "give me either a deep-immutable directory if possible, or a
> mutable directory to which the write key has been discarded" so that
> one can bundle a given set of caps without worrying about what their
> types are.


I'm thinking of a variant of "cp -r" for both of these.. maybe "cp -r
--immutable", which will re-use any immutable objects that it finds
(both files and immutable directories). Maybe --readonly would mean the
discarded-writecap form.

"cp -r --immutable" is thus the "virtual CD" creation command.

I like the idea of DeepImmutable directories, specifically so that a
tool like this can safely know whether it can re-use the object or not.
If deep-immutable directories are common, then this tool could save a
lot of time by not descending into any ones that it encounters.

My hunch is that there are more use cases for deep-immutable than
shallow-immutable, so I'd prefer it to be the default.


cheers,
 -Brian