## Refs

Like git, OSTree uses "refs" to which are text files that point to particular commits (i.e. filesystem trees). For example, the gnome-ostree operating system creates trees named like `gnome-ostree/buildmaster/x86_64-runtime` and `gnome-ostree/buildmaster/x86_64-devel-debug`. These two refs point to two different generated filesystem trees. In this example, the "runtime" tree contains just enough to run a basic GNOME system, and "devel-debug" contains all of the developer tools.

The ostree supports a simple syntax using the carat `^` to refer to the parent of a given commit. For example, `gnome-ostree/buildmaster/x86_64-runtime^` refers to the previous build, and `gnome-ostree/buildmaster/x86_64-runtime^^` refers to the one before that.