Git: Create repo as submodule

Question

I'd like to create a new repository as a submodule of my project.

Usually, I create a Github repo and then add it as a submodule using the command git submodule add url_to_repo.git

Is there a way to create a new repo directly as a submodule without creating the repo somewhere else first (neither locally nor remote e.g. on Github)?

Answer 1

Easy! Say submodule_dir is the name of the directory you wish to submodule-ize (assuming it's not already under git control).

cd submodule_dir
git init
git add .
git commit
# on github, create the new repo, then:
git remote add origin [email protected]:your_username/your_repo_name.git
git push -u origin master
cd ..
mv submodule_dir submodule_dir_delete_me
git submodule add [email protected]:your_username/your_repo_name.git submodule_dir

Later (once you're happy)

rm -rf submodule_dir_delete_me

• user2420206: This worked for me great when I wanted to add a new folder as a new submodule. If anyone makes a mistake, like I did, and puts in the wrong path to the submodule_dir , in the git submodule add, then that can be fixed by the command of git mv wrong_path correct_path and git will fix up the submodule plumbing automatically, as well as move the submodule. (this mv a submodule requires > git version 1.8.5)
• Milack27: For me it worked even without the mv. When I executed the git submodule add, git just added the existing repo at submodule_dir to the index of the parent repo. So there was no need of cloning the submodule and deleting the old folder.

Answer 2

I don't see how you could: a submodule is by definition a SHA1 from another repo (ie the other repo must exist for the parent repo to extract said SHA1): you must have its address referenced in the .gitmodules file that you keep in the parent repo.

Submodules are composed from a so-called gitlink tree entry in the main repository that refers to a particular commit object within the inner repository that is completely separate.

submodule.<name>.url

Defines a URL from which the submodule repository can be cloned. This may be either an absolute URL ready to be passed to git-clone(1) or (if it begins with ./ or ../) a location relative to the superproject's origin repository.

So you could create the submodule repo locally, but you must create it anyway.

• manuels: How about git init .; mkdir a; cd a; git init .; cd..; git submodule add ./a a or is it a bad idea?
• VonC: @manuels That's what I just added in my answer, but the point is: you must create a repo for you to be able to reference it in a parent repo as a submodule. However, I don't see how it would play out once your parent repo is pushed to GitHub and clone by another user.
• manuels: so it's fine if I create the repo in the directory of the super-repo and use this dir as a submodule?
• VonC: @manuels yes: you can declare a submodule which is a nested repo of the main repo. The thing is: anyone cloning your main repo (that you owuld have pushed to GitHub) won't have access to your nested repo (even if pushed to GitHub too), because the ./myNestedRepo url will refer to an empty directory on their local workstation
• Thibault D.: It plays out if you're too lazy to login to github (or offline) and want to create you submodule NOW and push it later.

Answer 3

If I understand you right this is what I'm frequently doing for eclipse projects and workspaces. Let's start with this structure:

$ find .
.
./projekt.txt
./sub1
./sub1/sub1.txt
./sub2
./sub2/sub2.txt

First initialize the submodules and master:

$ cd sub1
$ git init
$ git add *
$ git commit -m "init sub1"
$ cd ../sub2
$ git init
$ git add *
$ git commit -m "init sub2"
$ cd ..
$ git init
$ git status
# On branch master
#
# Initial commit
#
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# projekt.txt
# sub1/
# sub2/

To add those folders as submodules instead of regular folders, simply do the following command, and use relative paths like ./sub instead of just sub

$ git submodule add ./sub1
$ git submodule add ./sub2

Now it should look like

$ git status
# On branch master
#
# Initial commit
#
# Changes to be committed:
# (use "git rm --cached <file>..." to unstage)
#
# new file: .gitmodules
# new file: sub1
# new file: sub2
#
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# projekt.txt

Finally do a git add * and git commit -m "init parent" on the parent folder and there you are!

If you now change a file in one of your submodules, you have to commit the submodules first and then the parent repository as well in order to get the latest versions of your submodules when someone clones your parent repo.

• nwp: If the submodule is in another folder like ./sub1/sub2 then git submodule add ./sub1/sub2 will clone sub2 into . which is not what you want. To fix that use git submodule add ./sub1/sub2 ./sub1/sub2. The first path specifies from where to add and the second where to add it to.
• Bakaburg: Uhm, I am getting the error: cannot add to the index - missing --add option? when I try to commit the .gitmodules and the submodule files...
• Bakaburg: solved, I had to commit first the .gitmodules file and then the subfolder