How to dynamical create a file with git info and include it in the the image and save it on build system

We have several developers working on a project. The areas we are concerned about (and we regularly modify) are kernel, our custom code, and the yocto space itself.

We'd like to create a file at some point in the process (do_fetch, or do_install?) that contains info about what's being built. Such as the git branch name and hash for each of the repos above. We would then install that file (or files if need be) onto the image as well as archive it away on a centralized server.

I know that some of this info is available in the buildhistory, but I'm not sure if it is there when we'd like to install and package.

Getting the branch and hash should be easy to get via shell commands in the recipe functions.

Before I go off and hack something out, I thought I'd ask if there is a standard way to do something similar to this.

Thanks!

Solution

In case you need to include custom information. A nice way consists in creating a custom layer bbclass, defined as follow :

DEPENDS += "git-native"

do_rootfs_save_versions() {
    #Do custom tasks here like getting layer names and linked SHA numbers
    #Store these information in a file and deploy it in ${DEPLOY_DIR_IMAGE}
}

ROOTFS_POSTPROCESS_COMMAND += "do_rootfs_save_versions;"

Then, include the bbclass in your image file

IMAGE_CLASSES += "<bbclass_name>"

It is very useful when you want to determine the layer version/image name/.. running on target.