[LLVMdev] svn mirror git?

David Blaikie dblaikie at gmail.com
Thu Nov 15 12:27:40 PST 2012

On Thu, Nov 15, 2012 at 12:01 PM, Greg Fitzgerald <garious at gmail.com> wrote:
> Hi Michael,
>> As for actually switching to git. I see no benefit to justify the cost
>> of switching unless we actually take advantage of git's features. And
>> I've yet to see anyone propose this.
> Then I'll be the first.  :)

I'd suggest you/others read the previous thread discussing this issue.
It's a bit tricky to link to a whole thread in the llvm-dev mail
archive, but here's one part of it:

> The benefit is that the review process would require no file copies or email
> attachments, shorter email conversations, no copying code during reviews to
> simulate inline comments, and no need to "git rebase" to push to the top of
> svn.  I wouldn't be surprised if the difference was so significant that
> folks would stop using the llvm-commits list altogether.  To see what
> changed, you'd check the github mirror, and to contribute you could post a
> link to llvmdev (not too noisy).

Essentially that's precisely what we want to avoid. The intention is
to keep discussion & review in the shared public view & keep the
codebase in a (mostly) singular state. The transition to git would
have to be justified on its merits while still preserving that
workflow, not while working against it.

(I'm not sure how folks would stop using llvm-commits all together, if
we still have as much shared development there would still be a push
email for every shared commit, an email for every review request, and
if the reduction in email was because review happened off-list, that
would be a loss, not a benefit)

> For example, say github's llvm-mirror was a contributor's fork.  The review
> process might look like this:
> Contributor:
>      Please review my patch:
> https://github.com/llvm-mirror/llvm/commit/4823be3be1d87632fbd51ce8e51a58ee5e44b115
> Maintainer:
>     Adds inline comments with online tool.  Then when patch is looking good:
>     $ git fetch https://github.com/llvm-mirror/llvm.git
>     $ git cherry-pick 4823be3be1d87632fbd51ce8e51a58ee5e44b115
>     $ git push
> Thanks,
> Greg
> On Thu, Nov 15, 2012 at 11:35 AM, Michael Spencer <bigcheesegs at gmail.com>
> wrote:
>> On Thu, Nov 15, 2012 at 10:48 AM, David Chisnall
>> <David.Chisnall at cl.cam.ac.uk> wrote:
>> >> > I think svn works better than git as an authoritative upstream
>> >>
>> >> Would you mind expanding on this?  What problem specifically is being
>> >> solved?  Linus and Guido both use DVCS's and the authoritative upstream is
>> >> whatever URL the BDFL says it is.
>> >
>> > Monotonic version numbers are the biggest advantage.  It is easy to see
>> > that r1234432 contains the bug fix introduced in r1234430. It is very hard
>> > to see if version 23bef194ac contains the bug fix added in 23bef19412.  This
>> > makes interaction with bugzilla and so on much easier.  If someone says
>> > 'please test r1245145 - should be fixed' you can easily check whether you
>> > are running r1245145 or newer.
>> >
>> > David
>> git branch --contains 23bef19412
>> This will tell you which of your branches have that commit and
>> highlight the current branch you are on.
>> Git also has monotonically increasing identifiers for each commit. The
>> time stamp. Which I find much more informative than a revision number
>> split between multiple repositories.
>> As for actually switching to git. I see no benefit to justify the cost
>> of switching unless we actually take advantage of git's features. And
>> I've yet to see anyone propose this. So for now, git-svn works for me.
>> - Michael Spencer
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