v0.19.1

What's Changed

• overlay: use umoci API for "add existing blob" by @tych0 in #248
• tests: use umoci API for adding a non-compressed blob by @tych0 in #249
• *: delete the btrfs storage backend by @tych0 in #250
• squashfs: fix squashtool url by @tych0 in #251
• Squashfs media type by @tych0 in #252
• deps: bump containerd version by @tych0 in #254
• Squashfs verity patches by @tych0 in #253
• ci: drop dead references to storage-type by @tych0 in #255
• api: add atomfs mount/umount APIs by @tych0 in #256
• atomfs: verify root hash for existing devices by @tych0 in #259
• atomfs: add test for AllowMissingVerityData by @tych0 in #260

Full Changelog: v0.18.0...v0.19.1