[Vm-dev] svn git bridge? (was: Spur corrupts large images when saving)

Eliot Miranda eliot.miranda at gmail.com
Sat Apr 23 17:35:39 UTC 2016


Hi Esteban, Hi Fabio,


On Apr 23, 2016, at 10:11 AM, Esteban Lorenzano <estebanlm at gmail.com> wrote:

> Hi,
> 
> I would like to have a list of constraints so we can sort it (otherwise this will never happen… :S)
> So far I have: 
> 
> - sqSCCSVersion.h adapt to git. In Pharo we already have something but I do not think is enough… I will take a look to this. 

> - do not break Cadence builds. AFAIK, nothing forbids jenkins to stop using SVN and start using GIT (we also use Jenkins for our builds and we didn’t found any problem)… someone has to do the change, but it should be fairly straightforward. Who is the person who can take this task? (I’d do it, but I suppose Cadence has access policy to that)

My colleague Bob Westergaard and I will have to do this.  There is no way Cadence will allow people from outside to do so ;-)

So I like Fabio's suggestion of deprecating subversion.  We can keep the subversion bridge for some time (6 months, 1 year?), announce when it is going away (if ever?) and give people time to transition.

> 
> what more?
> 
> (please, take into account that this is very important for us, and that I personally will be in a better position to go back to the trunk, and then contribute back my changes, that’s why I’m pushing it)

And having you, and others, contribute is really important to me too.  That's why I'm supporting this.

So another thing to discuss and then define is what's the process for updating the master repository?  I've not used github to do this so I need educating.  I presume:

- there is a set of trusted developers who have permission to integrate
- there is a smaller set of administrators who can redefine the set of trusted developer
- there is a commonly used pattern for differentiating between a version of the repository that exists to be built by and tested by slaves, and a version that has built and passed the tests satisfactorily 

> Esteban
> 
> ps: As far as I understood, Fabio didn’t said “next thursday”, but “one thursday” :)

Oops.  I should read these messages wearing sunglasses...  Sorry


>> On 23 Apr 2016, at 18:54, Eliot Miranda <eliot.miranda at gmail.com> wrote:
>> 
>> Hi Fabio,
>> 
>> 
>>> On Apr 23, 2016, at 9:40 AM, Fabio Niephaus <lists at fniephaus.com> wrote:
>>> 
>>> Hi all,
>>> 
>>> Bert already mentioned that I've been working on migrating the repository from SVN to Git.
>>> I believe there are three problems that need to be solved here:
>>> 
>>> 1. Migrating SVN externals for sharing code between branches
>>> This is currently used to share a few directories (e.g. platforms/Cross/plugins) across different
>>> branches. But Git does no support this kind of code sharing. Instead, it supports submodules [1]
>>> and subtrees [2]. I would suggest to move code that we want to share into separate Git
>>> repositories and include them as submodules. I think submodules are easier to understand
>>> (GitHub integrates them nicely in their UI). The only drawback: if someone updates code in a
>>> shared repository, one needs to update all references to this repository as well. But I'd say this
>>> is also a good thing: if someone changes e.g. a plugin and the change is compatible to Cog,
>>> but incompatible to the interpreter vm, then the interpreter branch is not automatically broken
>>> as soon as one pushes the plugin change. If the above is unclear, I'm happy to explain
>>> submodules in more detail.
>>> 
>>> 2. Versioning and new releases
>>> If we migrate to Git, I'd recommend to deprecate the way we do versioning in SVN. Instead, we
>>> should use Git commit hashes and Git tags. 
>> 
>> But have you modified platforms/Cross/vm/sqSCCSVersion.h to capture this information?  If so, can you please send me the code so I can integrate it?  If not, why not?
>> 
>>> Let's say we want to release a new version, we tag
>>> the commit of interest with e.g. v1.0.0. When building the Cog VM on this tag, the version will be
>>> v1.0.0. If we use GitHub, we might as well use a CI service such as Travis CI [3] to automate the
>>> build process. That means, each time someone pushes changes to GitHub, Travis CI will build a
>>> new Cog VM (we can call this "bleeding edge"). Let's say I push changes right after the release
>>> of v1.0.0, the version for the next build will be something like v1.0.0-37553a9 with "37553a9"
>>> being the short SHA1 identifying my latest commit. If we want to release e.g. v1.1.0, we just tag
>>> a newer commit and GitHub/Travis CI does the rest for us. I already have this working, you can
>>> find a Travis build at [4] and the result at [5]. Obviously, we can push the binaries to a different
>>> server.
>>> 
>>> 3. Keeping a copy of the code
>>> We of course want to keep a copy of our code at all times in case something happens with
>>> GitHub. There are already tools that we can use to automate this. However, I wouldn't try to keep
>>> the old SVN repository in sync. I believe this might be quite difficult and I don't see a reason to
>>> maintain something we want to deprecate in the first place. Anyway, it should be fairly easy to
>>> set up a tool that creates a backup on one of our servers whenever we change code on GitHub.
>>> 
>>> 
>>> Doing a migration from SVN to Git(Hub) takes a few hours and I'd recommend we stop pushing
>>> code to the SVN as soon as we start to migrate. This obviously requires everyone working with
>>> the code base to switch to Git. So please let me know if everyone is comfortable with the
>>> migration. If we want to do this next week, I'd recommend to do it on a Thursday or a Friday,
>>> because I would be able to do it with Bert sitting two rooms next to me :)
>> 
>> I'm not happy to migrate until there's a functional subversion bridge that works and doesn't break my builds.  Cadence pays for my time (and hence pays for a lot of the VM development we enjoy) and its builds use Jenkins and subversion and I will not cooperate with any effort that sabotages this.  "Next Thursday" doesn't appear to appreciate the constraints.  This has to be done carefully or I will not cooperate.
>> 
>> 
>>> 
>>> I hope I have thought about the important things and I'm happy to answer any questions you
>>> might have.
>>> 
>>> Best,
>>> Fabio
>>> 
>>> [1] https://git-scm.com/book/en/v2/Git-Tools-Submodules
>>> [2] http://blogs.atlassian.com/2013/05/alternatives-to-git-submodule-git-subtree/
>>> [3] http://travis-ci.org
>>> [4] https://travis-ci.org/fniephaus/squeak/builds/119507180
>>> [5] https://www.hpi.uni-potsdam.de/hirschfeld/artefacts/cog/v0.1.0/
>>> 
>>> 
>>> 
>>> -- 
>>> 
>>>> On Sat, Apr 23, 2016 at 5:10 PM David T. Lewis <lewis at mail.msen.com> wrote:
>>>> 
>>>> On Sat, Apr 23, 2016 at 02:22:29PM +0200, Nicolas Cellier wrote:
>>>> >
>>>> > 2016-04-23 13:56 GMT+02:00 Cl??ment Bera <bera.clement at gmail.com>:
>>>> >
>>>> > >
>>>> > > On Sat, Apr 23, 2016 at 12:54 PM, Bert Freudenberg <bert at freudenbergs.de>
>>>> > > wrote:
>>>> > >
>>>> > >>
>>>> > >> Actually, Fabio did a complete migration while squeakvm.org was out.
>>>> > >> This had a full history of all SVN commits.
>>>> > >>
>>>> > >> ???Unfortunately??? Ian fixed the server too soon so development continued on
>>>> > >> SVN, so now the git repo is again out-of-date.
>>>> > >>
>>>> > >> We would need to freeze the SVN, do the migration again, and use git from
>>>> > >> that point on. It would involve a day of downtime, but doing this sooner
>>>> > >> than later would be a good thing.
>>>> > >>
>>>> > >>
>>>> > doesn't gitsvn help?
>>>> >
>>>> 
>>>> I have to admit that I did not even know that an active git svn bridge
>>>> was possible. It sounds like this it might be very helpful.
>>>> 
>>>> It would be great to have the advantages of git for development, and
>>>> it could also be helpful to be able to have the squeakvm.org repo updated
>>>> periodically from git. There are portions of the platforms tree that Eliot
>>>> has been able to make identical for oscog and trunk, and this seems like
>>>> a worthwhile effort to continue.
>>>> 
>>>> Another possible advantage is that Ian's cmake build process takes advantage
>>>> of the SVN revision numbering, and it would be good to make sure this stays
>>>> healthy as development proceeds (it's a lot nicer than autotools).
>>>> 
>>>> Eliot, do you have a view on this?
>>>> 
>>>> Dave
>> 
>> _,,,^..^,,,_ (phone)
> 
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