> > Let me illustrate. Suppose these generations: > > > A ------> B ------> C > > > When doing a roll-back from C, one should obviously get back at B. At > > that point, C would still be available. Keeping it around means that > > users can easily switch back to C if B turned out to be less > > appropriate (this answers questions (1) and (2)). > > > Once at B, installing or removing packages would delete C, thus > > allowing its generation number to be reused, and create a new > > generation C’ with the same generation number as C: > > > A ------> B ------> C’ > > > At this point, switching back to C is no longer possible.
I agree too. Plus, it seems like a neat mechanism. I guess a generation would only be destroyed at a junction, not when moving back and forth in straight lines. A ------> B ------> C You could travel from C back to A and back to C without having to re-install packages... Looking forward to seeing it implemented. Alex On Fri, 25 Jan 2013, 02:44:39 GMT, Nikita Karetnikov <nik...@karetnikov.org> wrote: > > 3. More generally, should the history of generations be linear, or > > should it be a DAG like Git commits? > > If the latter is the case, then we can probably use a simple tree. Here > is a related link: [1]. > > > Regarding (3), it seems that a linear history not only simplifies the > > implementation, but also the user interface, while covering most > > practical use cases. > > I agree. > > > Let me illustrate. Suppose these generations: > > > A ------> B ------> C > > > When doing a roll-back from C, one should obviously get back at B. At > > that point, C would still be available. Keeping it around means that > > users can easily switch back to C if B turned out to be less > > appropriate (this answers questions (1) and (2)). > > > Once at B, installing or removing packages would delete C, thus > > allowing its generation number to be reused, and create a new > > generation C’ with the same generation number as C: > > > A ------> B ------> C’ > > > At this point, switching back to C is no longer possible. > > I like the idea. > > Nikita > > [1] http://learnyouahaskell.com/zippers#a-very-simple-file-system
