daemon/deploy: allow redeploying livefs booted commit

Also something I noticed while working on #981. When sitting on a livefs
commit, once a user does `rpm-ostree cleanup --pending --rollback`, it's
impossible to redeploy the same booted commit. Let's allow users to do
this.

Closes: #984
Approved by: cgwalters

src/daemon/rpmostreed-transaction-types.c

@@ -814,7 +814,23 @@ deploy_transaction_execute (RpmostreedTransaction *transaction,
                                                  &base_changed, cancellable, error))
         return FALSE;
 
-      changed = changed || base_changed;
+      if (base_changed)
+        changed = TRUE;
+      else
+        {
+          /* If we're on a live deployment, then allow redeploying a clean version of the
+           * same base commit. This is useful if e.g. the pushed rollback was cleaned up. */
+
+          OstreeDeployment *deployment =
+            rpmostree_sysroot_upgrader_get_merge_deployment (upgrader);
+
+          gboolean is_live;
+          if (!rpmostree_syscore_deployment_is_live (sysroot, deployment, &is_live, error))
+            return FALSE;
+
+          if (is_live)
+            changed = TRUE;
+        }
     }
 
   /* let's figure out if those new overrides are valid and if so, canonicalize

tests/vmcheck/test-livefs.sh

@@ -110,6 +110,12 @@ vm_cmd cat /etc/test-livefs-with-etc.conf > test-livefs-with-etc.conf
 assert_file_has_content test-livefs-with-etc.conf "custom"
 echo "ok livefs preserved modified config"
 
+vm_rpmostree cleanup -p
+# make sure there's no layering going on somehow
+vm_assert_status_jq '.deployments[0]["base-checksum"]|not'
+vm_rpmostree deploy $(vm_get_booted_deployment_info checksum)
+echo "ok livefs redeploy booted commit"
+
 reset
 vm_rpmostree install /tmp/vmcheck/yumrepo/packages/x86_64/foo-1.0-1.x86_64.rpm
 vm_rpmostree ex livefs