doc/treefile.md: New file

doc/treefile.md

@@ -0,0 +1,32 @@
+Treefile
+--------
+
+ * `ref`: string, mandatory: Holds a string which will be the name of
+   the branch for the content.
+
+ * `gpg_key` string, optional: Key ID for GPG signing; the secret key
+   must be in the home directory of the building user.  Defaults to
+   none.
+
+ * `repos` array of strings, mandatory: Names of yum repositories to
+   use, from the system `/etc/yum.repos.d`.
+
+ * `selinux`: boolean, optional: Defaults to `true`.  If `false`, then
+   no SELinux labeling will be performed on the server side.
+
+ * `bootstrap_packages`: Array of strings, mandatory: The `glibc` and
+   `nss-altfiles` packages (and ideally nothing else) must be in this
+   set; rpm-ostree will modify the `/etc/nsswitch.conf` in the target
+   root to ensure that `/usr/lib/passwd` is used.
+
+ * `packages`: Array of strings, mandatory: Set of installed packages.
+   Names prefixed with an `@` (e.g. `@core`) are taken to be the names
+   of comps groups.
+
+ * `units`: Array of strings, optional: Systemd units to enable by default
+
+ * `include`: string, optional: Path to another treefile which will be
+   used as an inheritance base.  The semantics for inheritance are:
+   Non-array values in child values override parent values.  Array
+   values are concatenated.  Filenames will be resolved relative to
+   the including treefile.