Git Submodules

A submodule pins a specific commit of an external repo. .gitmodules stores URL+path; the super tree records the SHA as a gitlink.

Cloning

git clone --recurse-submodules <url>       # preferred
git submodule update --init --recursive    # after a plain clone

Plain clone creates empty dirs. update without --init silently skips new ones.

Default Update = Detached HEAD

git submodule update checks out the pinned SHA detached. Work there is lost on next update unless committed to a branch.