When rebasing, prune previous container by default

When using `rpm-ostree rebase` on ostree branch names, by
default we prune the previous branch/ref to avoid leaking
space (i.e. requiring the user/admin to manually prune it).
We do have the `--skip-purge` option to suppress this behavior.

When we added the container bits, we ignored this at the time.
But we really need to do this by default, for the same reasons
around avoiding space leakage.

rpmostree-cxxrs.cxx

@@ -2059,6 +2059,10 @@ extern "C"
   ::rust::repr::PtrLen rpmostreecxx$cxxbridge1$query_container_image_commit (
       const ::rpmostreecxx::OstreeRepo &repo, ::rust::Str c,
       ::rust::Box< ::rpmostreecxx::ContainerImageState> *return$) noexcept;
+
+  ::rust::repr::PtrLen
+  rpmostreecxx$cxxbridge1$purge_refspec (const ::rpmostreecxx::OstreeRepo &repo,
+                                         ::rust::Str refspec) noexcept;
   ::std::size_t rpmostreecxx$cxxbridge1$TempEtcGuard$operator$sizeof () noexcept;
   ::std::size_t rpmostreecxx$cxxbridge1$TempEtcGuard$operator$alignof () noexcept;
   ::std::size_t rpmostreecxx$cxxbridge1$FilesystemScriptPrep$operator$sizeof () noexcept;
@@ -3618,6 +3622,16 @@ query_container_image_commit (const ::rpmostreecxx::OstreeRepo &repo, ::rust::St
   return ::std::move (return$.value);
 }
 
+void
+purge_refspec (const ::rpmostreecxx::OstreeRepo &repo, ::rust::Str refspec)
+{
+  ::rust::repr::PtrLen error$ = rpmostreecxx$cxxbridge1$purge_refspec (repo, refspec);
+  if (error$.ptr)
+    {
+      throw ::rust::impl< ::rust::Error>::error (error$);
+    }
+}
+
 ::std::size_t
 TempEtcGuard::layout::size () noexcept
 {

rpmostree-cxxrs.h

@@ -1764,6 +1764,8 @@ pull_container (const ::rpmostreecxx::OstreeRepo &repo,
 ::rust::Box< ::rpmostreecxx::ContainerImageState>
 query_container_image_commit (const ::rpmostreecxx::OstreeRepo &repo, ::rust::Str c);
 
+void purge_refspec (const ::rpmostreecxx::OstreeRepo &repo, ::rust::Str refspec);
+
 ::rust::Box< ::rpmostreecxx::TempEtcGuard> prepare_tempetc_guard (::std::int32_t rootfs);
 
 ::rust::Box< ::rpmostreecxx::FilesystemScriptPrep>

rust/src/lib.rs

@@ -199,6 +199,7 @@ pub mod ffi {
             repo: &OstreeRepo,
             c: &str,
         ) -> Result<Box<ContainerImageState>>;
+        fn purge_refspec(repo: &OstreeRepo, refspec: &str) -> Result<()>;
     }
 
     // core.rs

rust/src/sysroot_upgrade.rs

@@ -154,3 +154,34 @@ pub(crate) fn query_container_image_commit(
     let state = ostree_container::store::query_image_commit(repo, imgcommit)?;
     Ok(Box::new(state.into()))
 }
+
+/// Remove a refspec, which can be either an ostree branch or a container image.
+pub(crate) fn purge_refspec(repo: &crate::FFIOstreeRepo, imgref: &str) -> CxxResult<()> {
+    let repo = &repo.glib_reborrow();
+    tracing::debug!("Purging {imgref}");
+    if let Ok(cref) = OstreeImageReference::try_from(imgref) {
+        // It's a container, use the ostree-ext APIs to prune it.
+        let iref = &cref.imgref;
+        ostree_container::store::remove_images(repo, [iref])?;
+        let n = ostree_container::store::gc_image_layers(repo)?;
+        tracing::debug!("Pruned {n} layers");
+    } else if ostree::validate_checksum_string(imgref).is_ok() {
+        // Nothing to do here
+    } else {
+        match ostree::parse_refspec(imgref) {
+            Ok((remote, ostreeref)) => {
+                repo.set_ref_immediate(
+                    remote.as_ref().map(|s| s.as_str()),
+                    &ostreeref,
+                    None,
+                    ostree::gio::NONE_CANCELLABLE,
+                )?;
+            }
+            Err(e) => {
+                // For historical reasons, we ignore errors here
+                tracing::warn!("{e}");
+            }
+        }
+    }
+    Ok(())
+}

src/daemon/rpmostreed-transaction-types.cxx

@@ -1597,19 +1597,9 @@ deploy_transaction_execute (RpmostreedTransaction *transaction, GCancellable *ca
         return FALSE;
 
       /* Are we rebasing?  May want to delete the previous ref */
-      if (self->refspec && !(deploy_has_bool_option (self, "skip-purge")))
+      if (self->refspec && !(deploy_has_bool_option (self, "skip-purge")) && old_refspec)
         {
-          g_autofree char *remote = NULL;
-          g_autofree char *ref = NULL;
-
-          /* The actual rebase has already succeeded, so ignore errors. */
-          if (old_refspec && ostree_parse_refspec (old_refspec, &remote, &ref, NULL))
-            {
-              /* Note: In some cases the source origin ref may not actually
-               * exist; say the admin did a cleanup, or the OS expects post-
-               * install configuration like subscription-manager. */
-              (void)ostree_repo_set_ref_immediate (repo, remote, ref, NULL, cancellable, NULL);
-            }
+          CXX_TRY (rpmostreecxx::purge_refspec (*repo, old_refspec), error);
         }
 
       /* Always write out an update variant on vanilla upgrades since it's clearly the most

tests/kolainst/destructive/container-image

@@ -57,6 +57,8 @@ case "${AUTOPKGTEST_REBOOT_MARK:-}" in
 
     rpm-ostree status | tee out.txt
     assert_file_has_content_literal out.txt 'Digest: sha256:'
+    ostree container image list --repo=/ostree/repo | tee imglist.txt
+    assert_streq "$(wc -l < imglist.txt)" 1
 
     v1=$(rpm-ostree status --json | jq -r '.deployments[0].version')
     assert_streq "${v0}" "${v1}"
@@ -163,6 +165,8 @@ EOF
     derived=oci:$image_dir:derived
     skopeo copy containers-storage:localhost/fcos-derived $derived
     rpm-ostree rebase ostree-unverified-image:$derived
+    ostree container image list --repo=/ostree/repo | tee imglist.txt
+    assert_streq "$(wc -l < imglist.txt)" 1
     rm $image_dir -rf
     /tmp/autopkgtest-reboot 3
     ;;