# submodule

A submodule is a git repository included inside another at a version fixed by the parent.

Submodules are used to factor out directories which are used in multiple repositories.

This approach is useful when there is no way to:

• share a file between programs (like PATH does for executable)
• maintain different versions of a program (like virtualenv does for Python)

for a given technology.

If a better system does exist for you repository however, e.g. Python / Ruby modules + virtualenv / RVM, use that method instead.

A submodule is a completely separate repo: the super repository only keeps note of its path, URL and current commit.

## Create a submodule

Create on directory .latex:

Modifies / creates .gitmodules, which you should then git commit.

If the directory exists and contains the required git repository already, nothing is done.

Else, the repository is cloned.

If your technology requires files to be in the current directory, you can use symlinks into the submodule to achieve that effect.

You have a LaTeX a.sty file which you want to use.

• on version 1.1 for a LaTeX project 2 in project2 repo
• on version 1.0 for a LaTeX project 3 in project3 repo

Make a repo and put a.sty in the repo. Call it latex.

On project 2:

ln -s shared/a.sty a.sty

Now the dir called shared was created and contains your repo.

## Clone a repo that contains a submodule

To get all the files of submodules you need the --recursive flag:

If you forgot to use recursive when you cloned, you should:

git submodule update --init

It seems that making clone recursive by default is neither possible nor a good idea: http://stackoverflow.com/questions/4251940/retrospectively-add-recursive-to-a-git-repo

## Update content of a submodule

cd share
git pull

Now from the main repository;

cd ..
git status
#modified:   shared (new commits)

For your repo to incorporate this update, you have to add the submodule path (share/) and commit, or simply do a commit -a next time.

From the outside, the submodule looks much like a regular git controlled file.

Update the contents of all submodules:

git submodule foreach git pull

This does not work if the modules are only listed under .gitmodule but have not been added to index with add.

## Update repository that contains as submodule

git pull
git submodule update

## foreach

Do an arbitrary command from each submodule directory.

git submodule foreach git pull

Print full paths of each submodule:

git submodule foreach pwd

## deinit

As of git 1.8.3:

git submodule deinit path

Files are kept and the .gitmodule file is not edited, but internally the module is removed and you can get rid of those.

Before 1.8.3: first remove it from the .gitmodules file:

vim .submodules

Then Remove it from .git/config:

vim .git/config

Then:

rm --cached $path_to_submodule #(no trailing slash). rm -Rf .git/modules/$path_to_submodule
git commit -am 'removed submodule'
rm -rf \$path_to_submodule

## Change submodule upstream

Edit .gitmodules and then:

git submodule sync
git submodule update

## Change submodule location

http://stackoverflow.com/questions/4604486/how-do-i-move-an-existing-git-submodule-within-a-git-repository