updog: new subcommand to revert 'update-apply'

Adds a new subcommand for reverting actions done by 'update-apply'.
Used to "deactivate" an update.

sources/updater/updog/src/main.rs

@@ -44,6 +44,7 @@ enum Command {
     Update,
     UpdateImage,
     UpdateApply,
+    RevertUpdateApply,
 }
 
 #[derive(Debug, Deserialize)]
@@ -92,6 +93,8 @@ SUBCOMMANDS:
     update-apply            Update boot flags (after having called update-image)
         [ -r | --reboot ]             Reboot after updating boot flags
 
+    revert-update-apply     Revert actions done by 'update-apply'
+
 GLOBAL OPTIONS:
     [ -j | --json ]               JSON-formatted output
     [ --log-level trace|debug|info|warn|error ]  Set logging verbosity");
@@ -266,6 +269,16 @@ fn update_flags() -> Result<()> {
     Ok(())
 }
 
+fn revert_update_flags() -> Result<()> {
+    let mut gpt_state = State::load().context(error::PartitionTableRead)?;
+    // This actually wipes all the priority bits in the inactive partition
+    gpt_state.cancel_upgrade();
+    // The update is still in the inactive partition so mark the inactive partition as valid
+    gpt_state.mark_inactive_valid();
+    gpt_state.write().context(error::PartitionTableWrite)?;
+    Ok(())
+}
+
 fn set_common_query_params(
     transport: &HttpQueryTransport,
     current_version: &Version,
@@ -567,6 +580,9 @@ fn main_inner() -> Result<()> {
                 initiate_reboot()?;
             }
         }
+        Command::RevertUpdateApply => {
+            revert_update_flags()?;
+        }
         Command::Prepare => {
             // TODO unimplemented
         }