From the git submodule manpage under sync: Synchronizes submodules' remote URL configuration setting to the value specified in .gitmodules. It will only affect those submodules which already have an url entry in .git/config (that is the case when they are initialized or freshly added). This is useful when submodule URLs change upstream and you need to update your local repositories accordingly.
Added by Ewoud Kohl van Wijngaarden almost 12 years ago
Sync git submodule before updating them
From the git submodule manpage under sync:
Synchronizes submodules' remote URL configuration setting to the
value specified in .gitmodules. It will only affect those submodules
which already have an url entry in .git/config (that is the case when
they are initialized or freshly added). This is useful when submodule
URLs change upstream and you need to update your local repositories
accordingly.