How to include a Git revision in constant your firmware at build time with PlatformIO.

This Drupal 8 article is obsolete.

Often there are components of a Drupal website that should not be located in the document root such as configuration files. It is convenient to keep these files in version control but outside of the Drupal root. By utilising Git subtrees, a Drupal installation root may be below the root of the main repository, and upstream changes to Drupal core conveniently merged with git read-tree.