问题
I've added 2 submodules to a project, subA and subB, in externals/subA and externals/subB.
Today another team member committed his code and when it is pulled, both subA and subB show detached head status when using git status within externals/subA and externals/subB.
I did git submodule update first and that reported no errors. I tried then git submodule init and git submodule update again but it did not change.
How can we get the submodules back to be in sync? What causes this for the submodules? This is first time problem has arised since we began. Thanks.
回答1:
A submodule is by definition checked out in detached HEAD: it represents a specific SHA1 recorded as a gitlink in the parent repo index.
See "git submodule update" in order to make sure a submodule is tracking a branch:
# add submodule to track master branch
git submodule add -b master [URL to Git repo];
# update your submodule
git submodule update --remote
# or (with rebase)
git submodule update --rebase --remote
来源：https://stackoverflow.com/questions/48555375/git-submodule-detached-head-state