If the location (URL) of the submodule has changed, then you can simply:
- Modify the
.gitmodules
file in the repo root to use the new URL. - Delete the submodule folder in the repo
rm -rf .git/modules/<submodule>
. - Delete the submodule folder in the working directory
rm -rf <submodule>
. - Run
git submodule sync
. - Run
git submodule update
.
More complete info can be found elsewhere: