How to add already cloned projects as submodules?

To add many submodules, I wrote this simple loop:

for repo in vim/bundle/*
do
  echo $repo
  pushd $repo
  url=$(git remote get-url $(git remote))
  echo $url
  popd
  git submodule add $url ./$repo
done

Obvious limitations I didn't bother fixing:

• don't need to change directory, pretty sure you can pass the git directory as an argument to commands
• git remote actually returns all remotes, not just the current, so script will break if there are multiple

I will add onto @neevek's answer, if you get the already exists in the index error, then you can try this version:

1. Remove every "already cloned repository" from cache:
   (Because there is already an object there that does not point to the repository as a submodule, and it has to be deleted from index first to prevent conflict. Your repositories' contents or index will not be deleted upon doing this)

   git rm --cached ./localrepo
   

2. Use git submodule add https//example.com/remoterepo ./localrepo, where ./localrepo is your existing git repository.

   • Note: You get the URL for remoterepo from localrepo/.git/config.
3. Repeat the second step for all your existing repositories that you want to add as submodules.
4. Now you can run git submodule foreach git pull to update all your subprojects.

If you have lots of submodules, you may want to write a small script to automate the second step.

Adding existing git repository as a submodule is the same as adding a new one.

1. First make the folder that contains all your git repositories as itself a git repository with git init.
2. Use git submodule add https//example.com/remoterepo ./localrepo, where ./localrepo is your existing git repository.
   • Note: You get the URL for remoterepo from localrepo/.git/config.
3. Repeat the second step for all your existing repositories that you want to add as submodules.
4. Now you can run git submodule foreach git pull to update all your subprojects.

You may want to write a small script to automate the second step if you have lots of submodules, which shouldn't be difficult.

Edit

The following is what I used for trying to reproduce the error mentioned in the comments. I triple checked the commands, and I still can't see the error:

git --version

mkdir submoduletest
cd submoduletest

git init --bare remote_repo_A
git init --bare remote_repo_B 

git clone remote_repo_A local_repo_A
git clone remote_repo_B local_repo_B

cd local_repo_A
echo "test commit on repo B" >> test.txt
git add test.txt
git commit -m 'test commit message'
git push origin master

cd ../local_repo_B
echo "test commit on repo B" >> test.txt
git add test.txt
git commit -m 'test commit message'
git push origin master

cd ../local_repo_A
git clone ../remote_repo_B local_repo_B
git submodule add ../remote_repo_B ./local_repo_B
git submodule foreach git pull origin master

git add .
git ci -m 'we just added a submodule for remote_repo_B'

git submodule status

Use the following command to check current status of local_repo_A, it has only two blob objects, one for 'test.txt' and another for the implicitly created '.gitmodules' file, nothing from remote_repo_B are added to the index of local_repo_A.

find .git/objects -type f | awk -F/ '{print $3$4}' | xargs -I {} git cat-file -t {} | grep blob

The reason I rolled back the edits is because the edits is simply WRONG, it was already rejected by two other mediators and me, but later some other guy approved it, I am not sure if it is a bug of SO or what. But the edits are rejected, even now because it's totally wrong, I already explained why in the comments, I am no offensive to anyone, but this wasted my time, downvote it if the answer is not helpful to you.

Again, if you are not improving it, DON'T edit my answer.