Re: [Monotone-devel] Moving monotone databases

[Derek Scherger]

Nathaniel Smith wrote:
> To make that a little more concrete --- it is mathematically
> impossible to do exactly what you want, because 1) you can't modify
> or get rid of a cert once it's issued, it's out there in everyone's
> database, so you can't reach out and change/eliminate all the existing
> branch certs, and 2) even if you just want to make duplicate branch
> certs with the new name, you can't preserve trust information.

I think there is another perspective that we can consider when thinking 
about the general concept of deleting things from a local monotone 
database, rather than from "the one true universal monotone database".

It is possible to merge several small local databases into one larger 
one by pushing them all to one common monotone server.

It is also possible to split one large database containing several 
branches into several smaller local databases by creating fresh local 
databases and pulling specific branches into them. This is made somewhat 
difficult at the moment by the concept of collections and would be 
easier if/when collections are dropped and servers serve globs of branches.

So, "deleting a branch" might just mean "remove it from my local 
database, because I'm not interested in it any more". Clearly it is very 
difficult to possible to remove things from the universal monotone 
database once they have been distributed.

Based on this does it not seem somewhat reasonable to have a command like

        monotone db remove branch foobar

to remove all branch certs with the value foobar in a local database?

There are definitely wrinkles with this though. I beleive it is an 
underlying assumption that every revision in a monotone database *must* 
have at least one branch cert. So what should happen to revisions that 
have only the foobar branch cert? Perhaps they should be removed, but if 
they have any descendents, dealing with the ancestry implications might 
be rather interesting. Removing revisions might leave manifests around 
that are no longer referenced by any revision and removing manifests 
might leave files around that are no longer referenced by any manifest 
so these need to be handled carefully.

Personally, I think I would like the ability to do things locally like 
remove and rename branches and to remove keys and possibly the ability 
to find and remove unreferenced manifests and unreferenced files as 
well. However, having some sort of "monotone db fsck" command to find 
and fix the associated problems might be a good first step.

Cheers,
Derek