test/petrify after petrifying:
{
    "name": "hello-system",
    "kind": "system",
    "arch": "x86_64",
    "strata": [
        {
            "morph": "hello-stratum",
            "repo": "test:morphs",
            "ref": "test/petrify"
        },
        {
            "morph": "stratum2",
            "repo": "test:external-strata",
            "ref": "test/petrify"
        },
        {
            "morph": "stratum3",
            "repo": "test:external-strata",
            "ref": "test/petrify"
        }
    ]
}
{
    "name": "stratum2",
    "kind": "stratum",
    "chunks": [
        {
            "name": "hello",
            "repo": "test:stratum2-hello",
            "ref": "f4730636e429149bb923fa16be3aa9802d484b23",
            "build-mode": "test",
            "build-depends": [],
            "unpetrify-ref": "master"
        }
    ]
}
{
    "name": "stratum3",
    "kind": "stratum",
    "chunks": [
        {
            "name": "hello",
            "repo": "test:stratum3-hello",
            "ref": "f4730636e429149bb923fa16be3aa9802d484b23",
            "build-mode": "test",
            "build-depends": [],
            "unpetrify-ref": "master"
        }
    ]
}

test/petrify after editing a chunk:
{
    "name": "hello-system",
    "kind": "system",
    "arch": "x86_64",
    "strata": [
        {
            "morph": "hello-stratum",
            "repo": "test:morphs",
            "ref": "test/petrify"
        },
        {
            "morph": "stratum2",
            "repo": "test:external-strata",
            "ref": "test/petrify"
        },
        {
            "morph": "stratum3",
            "repo": "test:external-strata",
            "ref": "test/petrify"
        }
    ]
}
{
    "name": "stratum2",
    "kind": "stratum",
    "chunks": [
        {
            "name": "hello",
            "repo": "test:stratum2-hello",
            "ref": "test/petrify",
            "build-mode": "test",
            "build-depends": []
        }
    ]
}
{
    "name": "stratum3",
    "kind": "stratum",
    "chunks": [
        {
            "name": "hello",
            "repo": "test:stratum3-hello",
            "ref": "f4730636e429149bb923fa16be3aa9802d484b23",
            "build-mode": "test",
            "build-depends": [],
            "unpetrify-ref": "master"
        }
    ]
}

test/unpetrify after unpetrifying:
{
    "name": "hello-system",
    "kind": "system",
    "arch": "x86_64",
    "strata": [
        {
            "morph": "hello-stratum",
            "repo": "test:morphs",
            "ref": "test/unpetrify"
        },
        {
            "morph": "stratum2",
            "repo": "test:external-strata",
            "ref": "test/unpetrify"
        },
        {
            "morph": "stratum3",
            "repo": "test:external-strata",
            "ref": "test/unpetrify"
        }
    ]
}
{
    "name": "stratum2",
    "kind": "stratum",
    "chunks": [
        {
            "name": "hello",
            "repo": "test:stratum2-hello",
            "ref": "test/petrify",
            "build-mode": "test",
            "build-depends": []
        }
    ]
}
{
    "name": "stratum3",
    "kind": "stratum",
    "chunks": [
        {
            "name": "hello",
            "repo": "test:stratum3-hello",
            "ref": "master",
            "build-mode": "test",
            "build-depends": []
        }
    ]
}