> ffmpeg is managed with svn; I like to track its development with git-svn.
> Works wonderfully except for one problem: they've made use of svn:externals
> for one component, libswscale. Previously I just regularly updated the
> libswscale subdirectory by checking out the latest copy (which is all that
> subversion does) and committing it to my own branch off upstream.
>
> With submodule support in git, it makes it possible to do a much better job.
> What I did was have two svn-remote sections in the config:
>
> [svn-remote "ffmpeg"]
> url = svn://svn.mplayerhq.hu/ffmpeg
> fetch = trunk:refs/remotes/ffmpeg-svn
>
> [svn-remote "libswscale"]
> url = svn://svn.mplayerhq.hu/mplayer
> fetch = trunk/libswscale:refs/remotes/libswscale-svn
>
> After running git-svn fetch; there are two independent branches in my
> repository:
>
> -- * -- * -- * -- * -- * (ffmpeg-svn)
> ---- * ----- * ------- * (libswscale-svn)
>
> Now, we fork from ffmpeg-svn and libswscale-svn to make non-tracking branches
> that can be committed to:
>
> $ git checkout -b master-ffm ffmpeg-svn
> $ git branch master-sws libswscale-svn
>
> Next, we create a shared clone of the repository as a subdirectory in that
> repository.
>
> $ git clone -s . libswscale
>
> Now we want that clone to be even more strongly linked to the parent - to the
> extent that they share the same refs, etc:
>
> $ cd libswscale
> $ rm -rf .git/refs .git/logs .git/info description config
> $ ln -s ../../.git/refs .git/refs
> $ ln -s ../../.git/logs .git/logs
> $ ln -s ../../.git/info .git/info
> $ ln -s ../../.git/config .git/config
> $ ln -s ../../.git/description .git/description
>
> Only HEAD and index are independent. Next we switch from the ffmpeg branch to
> the libswscale branch in this subdirectory:
>
> $ git checkout master-sws
>
> Now, we make the subdirectory a submodule in the parent:
>
> $ cd ..
> $ git add libswscale
> $ git commit -m "libswscale is now a submodule"
>
> How dangerous is this? I've made the repository it's own submodule and it
> shares the same refs, info and logs. LIVING ON THE EDGE MAN!
>
> You have to run two git-svn commands to sync with upstream:
>
> $ git-svn fetch ffmpeg
> $ git-svn fetch libswscale
>
> Then of course you would merge
>
> $ git merge ffmpeg-svn
> $ cd libswscale; git merge libswscale-svn; cd ..
> $ git commit -m "Sync with upstream"
>
> Personally I think that's pretty cool, this is significantly better than
> svn:externals because the particular revision of libswscale in use is
> recorded. Seriously - someone show me another VCS that can do that - I think
> git has actual magic powers :-)
>
> I dare say that git-svn could do much better because it could reconstruct the
> submodule history based on the repository dates and create the link in the
> tracking branch rather than having to do it manually at the end as I've done
> here. That would mean that the recorded submodule was right for all
> history - again, not the case for svn:externals, if you check out a previous
> version the external remains current.
>
>
>
> Andy
> --
> Dr Andy Parkins, M Eng (hons), MIET
>
andyparkins@gmail.com
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