When you run eas build, we need to get your source code from your development machine to one of our macOS or Linux build workers. In order to do this, EAS CLI will collect and compress project files into a single archive, and then upload that archive to private cloud storage that is accesible only to the build worker. By default, EAS CLI will produce the archive by performing a shallow git clone of your project and then compressing the cloned directory with tar.
You likely do not want to upload your node_modules directory, or maybe you have a .env file that is ignored by source control. Because EAS CLI uses does shallow git clone of your project before compressing it, your .gitignore configuration will be leveraged, and only files that are included in the latest commit will be included in the archive.
You can test this on your development machine against your local project directory by running the following command:
# Replace paths below with paths that make sense for your machine / operating system
git clone --local --no-hardlinks --depth 1 file:///path/to/your/git/repo- ~/path/to/clone/to
Alternatively, a fresh git clone from your remote would also be sufficient.
Environment variables are easy enough to handle, you can set those values using Secrets; but, in some cases, your build may depend on files that you consider sensitive and do not want to commit to source control.
In these cases, you can encode the contents of the file with base64, save that string as secrets, and then create the file in an EAS Build hook. See "How to use Git submodules" for an example. Alternatively, you can opt out of using Git and use .easignore instead.
You can set the EAS_NO_VCS=1 environment variable to skip using Git for all EAS CLI commands. When generating the archive with this variable set, EAS CLI will look for a .easignore file, which follows the same format as .gitignore. If no .easignore file is present in the project root, it will fallback to using the .gitignore.