remove a git submodule

Let’s say that you have a submodule in your project called ’submodule1′ and it’s in the following path: ‘vendors/submodule1′. In git there are 3 traces of this this submodule:
1) .gitmodules
2) .git/config
3) the submodule entry in the index/commit itself.

To remove the first two, is really simple, you just edit those files and remove the lines that specify the submdoule. In order to delete the third and last trace of the submodule in git, you need to type the following command:
git rm --cached path/to/submodule
Note: Do not put a trailing slash at the end of path. If you put a trailing slash at the end of the command, it will fail.

UPDATE a submodule

On the other hand, sometimes you are going to want to track a more recent revision. How do you do that? Well, just the same as we do with another git repository (because this is a fully fledged git repository!):

mathie@tullibardine:books$ cd vendor/plugins/rspec/
mathie@tullibardine:rspec$ git remote update
Updating origin
mathie@tullibardine:rspec$ git merge origin/master
Already up-to-date.

(Unfortunately, I’m writing this in realtime and there were no changes to pull since I started writing it!) That will pull the latest version of RSpec from github and update your local repository. Once you’ve done that, change back into the root of your project and do a git stat:

mathie@tullibardine:rspec$ cd ../../..
mathie@tullibardine:books$ git stat
# On branch master
# Changed but not updated:
#   (use "git add ..." to update what will be committed)
#
#   modified:   vendor/plugins/rspec
#
no changes added to commit (use "git add" and/or "git commit -a")