How to update git submodule who's history was rewritten

Question

Say I have a git submodule already setup, and the upstream commit history has rewritten (for example a rebase squash was preformed).

Say the commit my submodule head is set to no longer exits. So I want to set the head hash submodule's repo's head. How do I do that?

Answer 1

You can simply go in the submodule, do a git fetch, and checkout the HEAD you need.

cd mysubmodule
git fetch
git checkout origin/abranch

Then you go back to the parent repo, add and commit that new submodule SHA1 entry.

Note that you also can convert a submodule in order to follow the latest commits of a branch.
In that case, a simple:

git submodule update --remote

would be enough.