Update cheatsheets

tldr/git-submodule

@@ -8,18 +8,30 @@ source: https://github.com/tldr-pages/tldr.git
 > Inspects, updates and manages submodules.
 > More information: <https://git-scm.com/docs/git-submodule>.
 
-- Install a repository's specified submodules:
+- View existing submodules, and the checked-out commit for each one:
+
+`git submodule status`
+
+- Install a repository's submodules (listed in `.gitmodules`):
 
 `git submodule update --init --recursive`
 
-- Add a Git repository as a submodule:
+- Add a Git repository as a submodule of the current one:
 
 `git submodule add {{repository_url}}`
 
-- Add a Git repository as a submodule at the specified directory:
+- Add a Git repository as a submodule of the current one, at a specific directory:
 
 `git submodule add {{repository_url}} {{path/to/directory}}`
 
 - Update every submodule to its latest commit:
 
 `git submodule update --init --recursive --remote`
+
+- Change the URL of a submodule:
+
+`git submodule set-url {{path/to/submodule}} {{new_url}}`
+
+- Unregister a submodule (e.g. before removing it from the repository with `git rm`):
+
+`git submodule deinit {{path/to/submodule}}`