Trigger a TeamCity build on changes in a git submodule

Question

How to setup TeamCity trigger to start build on changes in git submodule?

Currently you have to update a submodule commit pointer to trigger a build in the main repository, so that TC will register a change in the main repository.

Update

The problem is the submodule should be always tracking a branch master. AFAIK this cannot be achieved through git itself. I just would like for the build to overcome git limitation in that matter.

Answer 1

This is not a neat solution but is achieves a goal to build a project with the tip of the submodule, and not needing to update submodule by hand. (A hook would probably do to)

Create a separate build configuration on with the submodule as the main repo, and setup a command line build step to clone a maste-repo, pull/update submodule and push the updated submodule pointer back to the master-repo.

rm -r master-repo
git clone [email protected]:xxx/master-repo.git
cd master-repo
git status
git submodule update --init 
git config -f .gitmodules submodule.submodule-repo.branch master
cd submodule-repo
git pull origin master
git status
cd ..
git add submodule-repo
git commit -m "sub module update"
git push origin master

I'm new to git so this probably can be optimized.

Answer 2

It is not possible to do that as TeamCity (and git) cannot know that there is an update. Submodule entry in a repo just points to a commit.

What would be an update to it? There can be multiple branches and commits from this commit. Only you can decide where the submodule is to be updated to.