Git submodules are used in this project to manage the various OE layers for reasons described in this document. See this article for an introduction to Git submodules.
There are a few issues that are commonly encountered decsribed below.
Git submodules are not checked out as branch, but simply a git version. The
first thing you should do when working on a submodule is check out the
appropriate branch, documented in the .gitmodules file. If you
forget to do this, you may get an error when pushing and then if you run
git branch, you'll discover you are on the (no branch) branch. To recover
from this situation, check out the branch you want to work on and then run
git reflog. This command will list recent commits which you can then
cherry-pick to your working branch. See this
article
for more information.
If you get a submodule merge conflict, run git reset \<sources/submodule\>
If the remote repository for a submodule changes, run git submodule sync to
synchronize the new remote information into your working directory. This problem
is most often noticed when the git submodule update command cannot find a
version.