[Python-Dev] Looking for VCS usage scenarios (original) (raw)

Brett Cannon brett at python.org
Mon Nov 3 22:56:33 CET 2008

On Mon, Nov 3, 2008 at 10:35, Thomas Wouters <thomas at python.org> wrote:

On Mon, Nov 3, 2008 at 18:57, Brett Cannon <brett at python.org> wrote:

On Sun, Nov 2, 2008 at 17:08, Gustavo Niemeyer <gustavo at niemeyer.net> wrote: > Hi Brett, > >> At this point I am looking for any suggestions for fundamental usage >> scenarios that I am missing from the PEP. If you think the few already >> listed are missing some core part of a VCS, please let me know. > > As an initial disclaimer, I use bzr in my daily routine. That said, > I'm sending below a few mostly unbiased high-level ideas, just based > on useful ways we explore the DVCS-aspect on our normal daily > workflow. > > == Coordinated development with dependent features == > > A variation on coordinated development, which is actually one of the > main motivators for DVCS. Branch A is evolving out of the mainline, > and it depends on a feature that is on branch B which is also not yet > integrated. Parallel development of both should be nicely supported. > I'm sure all DVCS will do that in a decent form, but figuring how this > works may be instructive and worth mentioning. > Since I have never seen that come up during Python's development I am going to leave it out. But I do see the benefit and how it might help with future work. Euhm, wut? It hasn't come up during Python's development because Python is being developed in a VCS with very limited branches :) I'm partial to VCS's with proper branching (as you know) and I've been using that mode of development for many years. I've done development and maintenance of multi-developer projects using both the CVS/SVN nonbranching approach and the typical DVCS branch-often approach using BitKeeper, Bazaar and Mercurial (as well as the sort-of one-off-branch Perforce approach where you can easily 'wrap' a single change but can't really do dependant changes) -- and whenever possible I use the branch-often approach with dependant branches all over the place, especially when working on large, complicated changes. Building them up out of separate 'components' requires a little more administration (you have to remember which branch to submit to) but it makes debugging, piecemeal discussion and batchwise integration a lot easier.

I know it isn't used because of what VCSs we have used, which is why I have no experience with it and feel uncomfortable using it as a necessary usage scenario to evaluate whether a DVCS is better than svn, and if so which one.

But then again, having one scenario that shows svn's weakness directly wouldn't hurt. I could see a scenario where I start to fix something in branch A, realize that a deeper issue needs to be fixed, leading to branch B, and then have branch A depend on branch B. Is that possible? Or is injecting branch dependencies like that not workable? If it doesn't work, then a branch A/B that a branch C is dependent on would also work as a scenario (e.g. reworking the testing framework where you are doing a bunch of different things at once that are culminating in a single new testing branch that collects everything).

Those sound like what you are getting after?

-Brett

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