[webkit-dev] Faster Git SVN updates

Eric Seidel eric at webkit.org
Tue Nov 30 14:59:55 PST 2010

I am of the impression that now any git user need only run:

git config --replace-all svn-remote.svn.fetch

in their get repo and updates will be faster.  I'm doing so now on the EWS
bots, and will fix any tooling issues in encounter.

I think it's time that we consider adding a "git" section to


On Tue, Nov 30, 2010 at 2:20 PM, Eric Seidel <eric at webkit.org> wrote:

> I've now posted a patch to fix update-webkit as well:
> https://bugs.webkit.org/show_bug.cgi?id=50273
> Once that lands, I'll move the EWS bots over to using this "new" setup.
>  Assuming those stay working, we can teach the tools to offer to fix "old"
> setups.
> -eric
> On Mon, Nov 22, 2010 at 4:58 PM, Ojan Vafai <ojan at chromium.org> wrote:
>> http://trac.webkit.org/changeset/72575 for having scm.py do the right
>> thing.
>> On Thu, Nov 18, 2010 at 4:11 PM, Eric Seidel <eric at webkit.org> wrote:
>>> OK.  Sounds we should make this setup default.  I'll see if we can't
>>> educate update-webkit and webkitpy/common/checkout/scm.py about detecting
>>> this setup and doing the right thing in that case.
>>> I'll file a separate bug about making scm.py's Git object use --no-rebase
>>> during dcommit.
>>> -eric
>>> On Thu, Nov 18, 2010 at 4:08 PM, Evan Martin <evan at chromium.org> wrote:
>>>> On Thu, Nov 18, 2010 at 3:36 PM, David Levin <levin at google.com> wrote:
>>>> >> It's some magical setup by which your git svn fetchs will be much
>>>> faser.
>>>> >>  But I've heard it's buggy?  Can lead to local repository corruption?
>>>> >> Can someone set me straight?
>>>> No magic, just standard git: complicated, but logical once you
>>>> understand how it works. :\
>>>> It means that both "git pull" and "git svn fetch" will be updating the
>>>> same branch.  When the latter sees the former has pulled down new
>>>> stuff (quickly, via the fast git protocol), it knows to rebuild its
>>>> metadata from the new stuff you fetched (rather than fetching it all
>>>> over again via the slow svn protocol).
>>>> There's a catch: if you "git svn fetch", that creates new commits
>>>> locally.  When you later "git pull", you get the commits that were
>>>> constructed by git.webkit.org, which don't match (due to differing
>>>> timestamps).  This may screw up rebase, but I believe it's smart
>>>> enough to recognize the commits are "the same" (applied the same diff;
>>>> in git jargon, they have the same patch-id).  In practice you don't
>>>> even run "git svn fetch" except when the git server is behind, so I
>>>> don't know if there are corner cases here that I haven't run into.  (I
>>>> also haven't tried this on Windows in a while -- kind of terrified of
>>>> git there, though I hear it works for others.)
>>>> In particular for bots that are not committing, I see no catch, other
>>>> than that they will be behind whenever git.webkit.org is behind.
>>>> >> The current git svn fetch is *super* slow.  Especially if you're
>>>> behind by
>>>> >> more than a day or two.
>>>> >> If there was a way to make this faster method safe, by wrapping it in
>>>> some
>>>> >> other (error-checking) command which knew how to fall back to git svn
>>>> >> rebase, etc. when necessary I would love to make it the default
>>>> method for
>>>> >> all WebKit get users.
>>>> I have instructed all Chrome git users to use this method since
>>>> (checking the commit history...) Feb 2009 and it seems to work for us.
>>>>  Note that you need git >= 1.6.1 or so for it to work properly.  I
>>>> also use this method for working on WebKit (though I've only committed
>>>> around 60 patches so I mostly use it for pulling down new code).
>>>> PS: our tools also run svn dcommit with "--no-rebase" to avoid
>>>> needlessly going out to svn again after committing.
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