Submodules and merge conflicts

Submodules and merge conflicts

[Henk]

We have a git repository with 2 submodules structured like this:
-Root
 -Src
    -Scripts [Submodule]
    -Kernel [Submodule]
    -Web

When someone makes changes in the Kernel submodule, the sha1 of the
submodule changes. This means that the repository that uses this submodule
also changes because the link to the submodule changes. This very often
causes confusion. Co-workers very often get merge-conflicts on the submodule
sha1 which are annoying and confusing.

The reason we like using submodules instead of having one larger repository
is that there are seperate teams working on each module. We also use other
version numbers voor the kernel and the appllications using the kernel.

Instead of using the sha1 of a specific revision in the submodule, I would
find it more logical to use a branch-name or tag. This way you can commit on
the submodule without having to commit the new submodule revision to the
main repository also.

I would like to hear your thoughts on this. Maybe we are using submodules
wrong, or maybe this is already possible.

Henk Westhuis

-- 
View this message in context: http://n2.nabble.com/Submodules-and-merge-conflicts-tp2951928p2951928.html
Sent from the git mailing list archive at Nabble.com.

Re: Submodules and merge conflicts

[Avery Pennarun]

On Thu, May 21, 2009 at 9:22 AM, Henk <henk_westhuis@hotmail.com> wrote:
> Instead of using the sha1 of a specific revision in the submodule, I would
> find it more logical to use a branch-name or tag. This way you can commit on
> the submodule without having to commit the new submodule revision to the
> main repository also.
>
> I would like to hear your thoughts on this. Maybe we are using submodules
> wrong, or maybe this is already possible.

The primary advantage of the git submodule code is the ability to lock
to a specific sha1.  If you don't want to do that, you're not going to
get much benefit from using submodules.

One option here is to simply skip the 'git submodule' altogether and
just have a script that checks out the other git repositories into
subdirs.  Then you have total control over which branches, etc are
included, the changes to the script (eg. to change which branch you
want to use) can be merged just like changes to anything else.

We do something in between on our internal projects: we use git
submodules to lock in the sha-1 (it's really valuable to know
*exactly* which version of everything was used in a particular
release), but we have scripts to auto-update the sha-1 for each
submodule to the tip of the right branches.

For some other projects, we also use the git-subtree tool I developed
(http://alumnit.ca/~apenwarr/log/?m=200904#30) but given that your
submodules are huge things like the Linux kernel, it's probably not
appropriate in your case.  You might want to look at it anyway in case
I'm wrong.

Have fun,

Avery