On 5/31/2013 12:32 AM, Mike Hommey wrote: [...] >> Option 1 is where I personally think it's worth investing effort. It >> means we'd need to set up an atomic bidirectional bridge between hg and >> git (which I'm told is doable, and there are even commercial solutions >> for this out there that may solve this for us). Assuming we solve the >> bridge problem one way or another, it would give us all the benefits >> listed above, plus developer tool choice, and we could roll this out >> incrementally w/o the need to change all of our infrastructure at once. >> I.e. our roll out could look something like this: >> >> 1. create a read only, official mozilla-central git mirror >> 2. add support for pushing to try with git and see the results in tbpl >> 3. update tbpl to show git revisions in addition to hg revisions >> 4. move to project branches, then inbound, then m-c, release branches, etc > > Another way to look at this would be to make the git repository the > real central source, and keep the mercurial branches as clones of it, > with hg-git (and hg-git supports pushing to git, too). > > This would likely make it easier to support pushing to both, although > we'd need to ensure nobody pushes octopus merges in the git repo.
Yup, could be, and IMO the main point is that we'd have a lot of flexibility here. >> Option 2 is where this discussion started (in the Tuesday meeting a few >> weeks ago, >> https://wiki.mozilla.org/Platform/2013-05-07#Should_we_switch_from_hg_to_git.3F). >> Since then I've had a number of conversations and have been convinced >> that a wholesale change is the less attractive option. The cost of a >> wholesale change will be *huge* on the infrastructure end, to a point >> where we need to question whether the benefits are worth the cost. I >> have also spoken with other large engineering orgs about git performance >> limitations, one of which is doing the opposite switch, going from git >> to hg. > > I bet this is facebook. Their usecase includes millions of changesets > with millions of files (iirc, according to posts i've seen on the git > list). I've promised not to mention names here, so I won't confirm nor deny... but the folks I've been talking to mostly have a repo that's a good bit less than a single order of magnitude larger than m-c, so a couple of hundred k files, not millions. And given the file count trend in m-c (see attached image for an approximation), that doesn't make me feel too good about a wholesale switch given the work involved in doing so. > Mike > -- jst
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