How can I specify a branch/tag when adding a Git submodule?

Question

How does git submodule add -b work?

After adding a submodule with a specific branch, a new cloned repository (after git submodule update --init

Answer 1

Git submodules are a little bit strange - they're always in "detached head" mode - they don't update to the latest commit on a branch like you might expect.

This does make some sense when you think about it, though. Let's say I create repository foo with submodule bar. I push my changes and tell you to check out commit a7402be from repository foo.

Then imagine that someone commits a change to repository bar before you can make your clone.

When you check out commit a7402be from repository foo, you expect to get the same code I pushed. That's why submodules don't update until you tell them to explicitly and then make a new commit.

Personally I think submodules are the most confusing part of Git. There are lots of places that can explain submodules better than I can. I recommend Pro Git by Scott Chacon.