Rewrite livefs

Now always based on an overlayfs:
ostreedev/ostree@f2773c1
This fixes a whole swath of problems with the previous design,
including the danger in replacing `/usr/lib/ostree-boot` which
broke booting for some people.

Further, we don't need to push a rollback deployment; the livefs
changes are always transient.  So now we store livefs state
in `/run` instead of in the origin file.

Since we're doing a rewrite, it's now in Rust for much more safety.

We also always work in terms of incremental diffs between commits;
the previous huge hammer of swapping `/usr` was way too dangerous.

rust/Cargo.toml

@@ -35,7 +35,6 @@ subprocess = "0.2.6"
 chrono = { version = "0.4.19", features = ["serde"] }
 libdnf-sys = { path = "libdnf-sys", version = "0.1.0" }
 
-
 [lib]
 name = "rpmostree_rust"
 path = "src/lib.rs"

rust/src/includes.rs

@@ -8,7 +8,6 @@ NOTICE: The C header definitions are canonical, please update those first
 then synchronize the entries here.
 !*/
 
-use crate::syscore::ffi::RpmOstreeOrigin;
 use libdnf_sys::DnfPackage;
 
 // From `libpriv/rpmostree-rpm-util.h`.
@@ -19,12 +18,3 @@ extern "C" {
         gerror: *mut *mut glib_sys::GError,
     ) -> libc::c_int;
 }
-
-// From `libpriv/rpmostree-origin.h`.
-extern "C" {
-    pub(crate) fn rpmostree_origin_get_live_state(
-        origin: *mut RpmOstreeOrigin,
-        out_inprogress: *mut *mut libc::c_char,
-        out_livereplaced: *mut *mut libc::c_char,
-    );
-}

rust/src/lib.rs

@@ -20,10 +20,12 @@ mod initramfs;
 pub use self::initramfs::ffi::*;
 mod lockfile;
 pub use self::lockfile::*;
+mod livefs;
+pub use self::livefs::*;
+mod ostree_diff;
+mod ostree_utils;
 mod progress;
 pub use self::progress::*;
-mod syscore;
-pub use self::syscore::ffi::*;
 mod testutils;
 pub use self::testutils::*;
 mod treefile;