README.md: Update installation/usage to reflect new treefile reality

README.md

@@ -16,8 +16,8 @@ generates potentially many filesystem trees.  It also has code to
 generate disk images and run smoketests.
 
 
-Setting up the autobuilder
---------------------------
+Installing and setting up a repository
+--------------------------------------
 
 There are packages available in the rpm-ostree COPR; you can also
 just "sudo make install" it.
@@ -28,13 +28,32 @@ Once you have that done, choose a build directory.  Here we'll use
  # cd /srv/rpm-ostree
  # mkdir repo
  # ostree --repo=repo init --mode=archive-z2
+
+
+Running rpm-ostree
+------------------
+
+The core "rpm-ostree" takes as input a "treefile".  There is a demo
+one in `src/demo-treefile.json`.
+
+ # rpm-ostree sometreefile.json
+
+All this does is use yum to download RPMs from the referenced repos,
+and commit the result to the OSTree repository, using the ref named by
+`ref`.
+
+You can export `/srv/rpm-ostree/repo` via any static webserver.
+
+Running the autobuilder
+-----------------------
+
+The autobuilder instead takes as input a `products.json` which
+generates multiple treefiles.  Try this:
+
  # ln -s /path/to/rpm-ostree.git/fedostree/products.json .
  # rpm-ostree-autobuilder autobuilder
 
 That will automatically poll every hour for changes in the RPMs
-referenced by the products.json file, commit them to the
-/srv/rpm-ostree/repo, and generate cached disk images in
-/srv/rpm-ostree/images.
-
-You can export /srv/rpm-ostree/repo (and images/, and builds/) via any
-static webserver.
+referenced by the `products.json` file, commit them to the
+`/srv/rpm-ostree/repo`, and generate cached disk images in
+`/srv/rpm-ostree/images`.