feat: initial commit for erofs support (#25)

* feat: initial commit for erofs support

Before this commit, only squashfs was supported.
However, there are other filesystems such as erofs that fit the same
theme, and additional filesystem support requires refactoring and
exposing a more generic filesystem interface.

pkg/fs/fs.go    - Filesystem interface
pkg/squashfs    - squashfs
pkg/erofs       - erofs
pkg/common      - filesystem-agnostic common routines
pkg/verity      - verity routines

Signed-off-by: Ramkumar Chinchani <rchincha@cisco.com>

* fix: disable "advanced/incompatible" features for now

Signed-off-by: Ramkumar Chinchani <rchincha@cisco.com>

* fix!: drop the double invalid '+' in layer media-type

BREAKING-CHANGE: the layer media-type no longer contains "+verity"

For a layer media-type, we add the fstype+compression+verity_present.
Only one '+' is allowed as per following RFC.
https://datatracker.ietf.org/doc/html/rfc6838#section-4.2

Instead just rely on "root_hash" annotation.

Signed-off-by: Ramkumar Chinchani <rchincha@cisco.com>

* test: add a stacker.yaml for tests

* fix: rebasing after Mike's changes

Signed-off-by: Ramkumar Chinchani <rchincha.dev@gmail.com>

* fix: some more refactoring

* fix: remove notify support from erofs

* fix: try a released stacker version

Signed-off-by: Ramkumar Chinchani <rchincha.dev@gmail.com>

---------

Signed-off-by: Ramkumar Chinchani <rchincha@cisco.com>
Signed-off-by: Ramkumar Chinchani <rchincha.dev@gmail.com>

Author: rchincha

.github/workflows/build.yaml

@@ -20,7 +20,7 @@ jobs:
           sudo apt-get update
           sudo apt-get install bats fuse3 make libcryptsetup-dev libgpgme-dev \
           libcap-dev lxc libdevmapper-dev libacl1-dev libarchive-tools \
-          squashfuse squashfs-tools
+          squashfuse squashfs-tools erofs-utils
       - name: setup lxc
         run: |
           chmod ugo+x $HOME

Makefile

@@ -12,7 +12,7 @@ VERSION_LDFLAGS=-X main.Version=$(MAIN_VERSION)
 BATS = $(TOOLS_D)/bin/bats
 BATS_VERSION := v1.10.0
 STACKER = $(TOOLS_D)/bin/stacker
-STACKER_VERSION := v1.0.0
+STACKER_VERSION := v1.1.0-erofs
 TOOLS_D := $(ROOT)/tools
 GOCOVERDIR ?= $(ROOT)
 
@@ -36,7 +36,7 @@ gotest: $(GO_SRC)
 
 $(STACKER):
 	mkdir -p $(TOOLS_D)/bin
-	wget --progress=dot:giga https://github.com/project-stacker/stacker/releases/download/$(STACKER_VERSION)/stacker
+	wget --progress=dot:giga https://github.com/rchincha/stacker/releases/download/$(STACKER_VERSION)/stacker
 	chmod +x stacker
 	cp stacker $(TOOLS_D)/bin/