fastboot: Implement helper commands for Virtual A/B.

This introduces two new commands to the fastboot protocol:

  - getvar snapshot-update-status - Return "none", "snapshotted", or
    "merging" depending on the current status set by the boot control
    HAL.
  - snapshot-update [cancel] - Cancel any pending snapshot-based updates
    via the boot control HAL. After this, the HAL should return
    MergeStatus::CANCELLED and "update-merge-status" should be "none".
    If no argument is specified, the snapshot-update-status is returned
    via an INFO response.

Bootloaders are expected to implement this in a manner consistent with
the boot control HAL.

Fastboot-based tooling should expect wipes of userdata to fail when
update-merge-status returns "merging". Thus, the force flag now cancel
any pending snapshots.

Bug: 139154945
Test: fastboot getvar snapshot-update-status
      fastboot snapshot-update cancel
      fastboot snapshot-update

Change-Id: Idc423fe7656b212e929e64eb0e6b85b453e0e8dc

1 files changed, 6 insertions, 0 deletions

diff --git a/fastboot/fastboot_driver.cpp b/fastboot/fastboot_driver.cpp
index b897182a2..6a5ad206a 100644
--- a/fastboot/fastboot_driver.cpp
+++ b/fastboot/fastboot_driver.cpp
@@ -122,6 +122,12 @@ RetCode FastBootDriver::SetActive(const std::string& slot, std::string* response
                       response, info);
 }
 
+RetCode FastBootDriver::SnapshotUpdateCommand(const std::string& command, std::string* response,
+                                              std::vector<std::string>* info) {
+    std::string raw = FB_CMD_SNAPSHOT_UPDATE ":" + command;
+    return RawCommand(raw, response, info);
+}
+
 RetCode FastBootDriver::FlashPartition(const std::string& partition,
                                        const std::vector<char>& data) {
     RetCode ret;