git-submodule/before-rebase hook

git-submodule/before-rebase hook

[justin]

I just discovered git-submodule today, and already I can see it making  
my life a lot easier. I develop several modules that are used in two  
different projects, and being able to check in changes from the  
submodule in either project is something I have been wanting to do for  
a while. But there is one shortcoming in git-submodule that I haven't  
figured out how to overcome... yet.

When I make a change to a submodule and push that change to the parent  
repository, the change appears to all other users of the repository as  
a modification to the submodule commit version. A few people at our  
company use 'git ci -a' to add all of their changes, and I'm afraid  
they are going to unknowingly revert the submodule back to a previous  
version. So my plan was to add a post-pull hook that does 'git  
submodule update --init', so that people who don't do development on  
the submodule will get updates every time they pull. Unfortunately  
though, there is no such hook in git. I thought post-merge was going  
to work, but most people at our company use 'git pull --rebase', and  
post-merge isn't called in that case. The post-checkout hook is  
called, but the pull hasn't been completed at that point, so updating  
the submodule doesn't work. Alas, if only there was a post-rebase hook.

Any ideas other than patching every employee's git source to add a  
post-rebase hook?

Thanks,
Justin

Re: git-submodule/before-rebase hook

[Andreas Ericsson]

justin wrote:
> I just discovered git-submodule today, and already I can see it making 
> my life a lot easier. I develop several modules that are used in two 
> different projects, and being able to check in changes from the 
> submodule in either project is something I have been wanting to do for a 
> while. But there is one shortcoming in git-submodule that I haven't 
> figured out how to overcome... yet.
> 
> When I make a change to a submodule and push that change to the parent 
> repository, the change appears to all other users of the repository as a 
> modification to the submodule commit version.

It shouldn't, unless you push the change into a non-bare copy of a checked
out submodule, but that would be rather insane as the submodule rather
than the superproject then gets to decide which version of the submodule
to use.

> A few people at our 
> company use 'git ci -a' to add all of their changes, and I'm afraid they 
> are going to unknowingly revert the submodule back to a previous 
> version.

Ah, now I see where you're coming from. After you issue "git pull" in
the submodule you have to sync the new version of the submodule to the
superproject using "git submodule sync".

> So my plan was to add a post-pull hook that does 'git submodule 
> update --init', so that people who don't do development on the submodule 
> will get updates every time they pull.

Ok, I didn't. Why do you pull into the submodules if you don't want to
sync the code so the superproject gets the benefit of the changes?

> Unfortunately though, there is no 
> such hook in git. I thought post-merge was going to work, but most 
> people at our company use 'git pull --rebase', and post-merge isn't 
> called in that case. The post-checkout hook is called, but the pull 
> hasn't been completed at that point, so updating the submodule doesn't 
> work. Alas, if only there was a post-rebase hook.
> 
> Any ideas other than patching every employee's git source to add a 
> post-rebase hook?
> 

Yes. Only pull in submodules if you intend to sync them afterwards.

-- 
Andreas Ericsson                   andreas.ericsson@op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231