Stephan Menzel wrote:
On Tue, Mar 27, 2012 at 10:52 AM, Joel de Guzman <joel@boost-consulting.com> wrote:
Ok, I open my challenge to you and any Git/Hg fans.
Again, all I want is to:
1) Extract this modular repo structure from Boost:
spirit boost spirit libs spirit
Easily doable
2) that can merge both ways (upstream and downstream to and from the boost SVN trunk); needless to say, with all the histories intact.
Not at all doable. As I said, one may be able to hack this or make it work but it's not a defined or supported way of working with it. And using such a system in a way that defies its intended way of being used is pointless and will only support those who claim git itself is not a good thing. Sure, you may be able to cut your fingernails with a chainsaw but life is just better and a little safer if you don't do it and it adds to the chainsaw's reputation to a way that it doesn't deserve.
Just because I could think of a way, here's a "cut your fingernails with a chainsaw" approach (excellent formulation by the way). Using multiple git repositories: - a git-svn mirror of the Boost trunk; - a subtree repository for just /boost/spirit - a subtree repository for just /libs/spirit - optionally, more subtree repositories; - the actual modular repo for Spirit, on which you do your work, To merge upstream (assuming you don't edit non-Spirit subtrees): (on modular repo) git-subtree-push to the /boost/spirit repo git-subtree-push to the /libs/spirit repo (on trunk mirror) git-subtree-pull from the /boost/spirit repo git-subtree-pull from the /libs/spirit repo git-svn-push to the Boost trunk To merge downstream: (on trunk mirror) git-svn-pull from the Boost trunk git-substree-push to the /boost/spirit repo git-substree-push to the /libs/spirit repo git-substree-push to the other subtree repos (on modular repo) git-subtree-pull from the /boost/spirit repo git-subtree-pull from the /libs/spirit repo git-subtree-pull from the other subtree repos It would need some scripts (perhaps triggers) to make it doable, and then it would still not be elegant, but I believe it could work. It would take some care because each commit must edit only a single subtree (I don't think the system would break otherwise, but you might introduce sibling commits with the same commit message as an artifact). I also expect new commits will appear in a different order after you merge upstream or downstream, i.e. stably sorted by subtree, but history will not be altered afterwards on either side of the "subtree bridge". This might need clarification---if so, please poke me. I've not implemented this idea, both because I'm short on time and because I think it's best to wait for insights of other people first. I wouldn't be surprised if the entire idea is hopeless for reasons I haven't thought of. As Daniel pointed out, the entire thing will be slightly easier to handle if people only contribute to Spirit through the modular git repo. -Julian