Question

I have a git repo with a dev and a master branch. Now I am trying to use a different revision of a submodule in each branch. So for example I do this:

git checkout master
cd submodule
git checkout v1.0
cd ..
git commit -a -m "now using submodule v1.0"
git checkout dev
cd submodule
git checkout v2.0
cd ..
git commit -a -m "let's try submodule v2.0"

Now after that I checkout the master branch and it seems the submodule in the master branch is also pointing to the v2.0 commit instead of v1.0.

I’ve read quite a lot about git submodules, but it still seems a bit abstract to me. Could anybody explain how to use a submodule properly in this particular case? (git version 1.7.3.1)

Thanks!

Answer 1

Just changing branches in the super-project isn’t going to change the contents in the submodule; the branch change will only change the super-project’s commit reference for its submodule. You need to do:

git submodule update

after checking out a branch in the super-project. The ‘update’ will change the submodule to reference the proper commit. Here is an example:

ebg@taiyo(84)$ git checkout master
M test1
Switched to branch 'master'
ebg@taiyo(85)$ git submodule update
Submodule path 'test1': checked out '16aff6eed3998f14eb96b4f61666b47160de0e6b'
ebg@taiyo(89)$ git checkout top-other
M test1
Switched to branch 'top-other'
ebg@taiyo(90)$ git submodule update
Submodule path 'test1': checked out 'af33fca078dbb1fa415f9ea7fafb1b92cad1c6ae'
ebg@taiyo(91)$ git status
# On branch top-other
nothing to commit (working directory clean)