machined/machinectl: add logic to show list of available images

This adds a new bus call to machined that enumerates /var/lib/container
and returns all trees stored in it, distuingishing three types:

        - GPT disk images, which are files suffixed with ".gpt"
        - directory trees
        - btrfs subvolumes

1 files changed, 1 insertions, 0 deletions

diff --git a/src/shared/btrfs-util.h b/src/shared/btrfs-util.h
index 28dbeb4e27..c8f798b6a6 100644
--- a/src/shared/btrfs-util.h
+++ b/src/shared/btrfs-util.h
@@ -28,6 +28,7 @@ int btrfs_subvol_make(const char *path);
 int btrfs_subvol_remove(const char *path);
 int btrfs_subvol_snapshot(const char *old_path, const char *new_path, bool read_only, bool fallback_copy);
 int btrfs_subvol_read_only(const char *path, bool b);
+int btrfs_subvol_is_read_only_fd(int fd);
 
 int btrfs_reflink(int infd, int outfd);