Git submodules

Aether’s source code relies on a few dependencies in order to run properly:

Armadillo
NetCDF
nlohmann JSON library

Aether manages these dependencies using git’s submodule capability. Submodules are their own repositories that are contained within a larger repository. Submodules can nest within other submodules and their contents can be edited and updated.

Verify your version of git

In order to get started, you will need to verify which version of git you have installed because git’s support for submodules has changed throughout its various releases. These instructions will work for releases equal to or newer than git 2.7. In order to verify which version of git you are using, type:

git --version

Adding a submodule to a repository

mkdir external
git submodule add https://github.com/nlohmann/json external/json

Modifying your git config to show the status of submodules

git config --global status.submoduleSummary true

Organization of the .gitmodules file

The submodules are defined in a dot file stored in the root directory of the repository, .gitmodules.

cat .gitsubmodules
[submodule "external/json"]
    path = external/json
    url = https://github.com/nlohmann/json

Cloning a repository and its submodules

git clone https://github.com/AetherModel/Aether.git
cd Aether
git submodule init
git submodule update

Removing a submodule from a repository

Temporary removal

git submodule deinit external/json

Permament removal

git submodule deinit external/json
git rm external/json
git commit -m "Removed json submodule"