git submodule 'fatal: No url found for submodule path ... in .gitmodules' or submodule directories empty after git clone. How do I fix it?

Cause: two different things. (a) Empty directories: git clone does not populate submodules unless asked, so the submodule paths exist but are empty until you initialise and update them. (b) 'No url found for submodule path': the repository has a submodule entry (a gitlink) in its tree but .gitmodules has no matching submodule.<name>.url, usually because the submodule was removed or added by hand incompletely, or .gitmodules was not committed. Fix: 1. For empty directories: git submodule update --init --recursive. For new clones use git clone --recurse-submodules <url>. To make commands follow submodules by default, git config --global submodule.recurse true (clone still needs its own flag). 2. If a URL changed upstream: edit .gitmodules, then git submodule sync --recursive and git submodule update --init --recursive. Sync copies the URL from .gitmodules into .git/config for already-registered submodules. 3. For the 'No url found' error, check git ls-files --stage | grep ^160000 to see gitlink entries and compare with .gitmodules. If the submodule should exist, add its entry: git config -f .gitmodules submodule.<name>.path <path> and submodule.<name>.url <url>, then commit .gitmodules. 4. If it should not exist, remove the stale entry: git rm --cached <path> (and delete the leftover directory and any .git/modules/<name> data), then commit. 5. Use git submodule add <url> <path> for new submodules so that .gitmodules and the index stay consistent, and commit both. Verify: git submodule status shows each submodule at a commit hash with no leading minus sign (a minus means not initialised) and the directories contain files. Sources: https://git-scm.com/docs/git-submodule https://git-scm.com/docs/gitsubmodules