test/sources: add checks for org.osbuild.ostree

Add basic checks for the ostree source, which includes a successful
pull of a commit, an empty source entry and one where the specified
commit is non-existant. For this create a simple commit in a ostree
repo is checked in. The commit was created via:

  mkdir "/tmp/data"
  echo "Hello World" > /tmp/data/hello.txt
  ostree init --repo test/data/sources/org.osbuild.ostree/data/repo \
              --mode=archive

  ostree commit --repo test/data/sources/org.osbuild.ostree/data/ \
                --branch "test/ostree" /tmp/data \
                --timestamp="1995-05-13 12:34:56 +0000"
This should give an commit with the following commit id:
  d6243b0d0ca3dc2aaef2e0eb3e9f1f4836512c2921007f124b285f7c466464d8

test/data/sources/org.osbuild.ostree/cases/empty.json

@@ -0,0 +1,6 @@
+{
+  "expects": "success",
+  "org.osbuild.ostree": {
+    "items": {}
+  }
+}

test/data/sources/org.osbuild.ostree/cases/missing_file.json

@@ -0,0 +1,12 @@
+{
+  "expects": "error",
+  "org.osbuild.ostree": {
+    "items": {
+      "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb": {
+        "remote": {
+          "url": "http://localhost/sources/org.osbuild.curl/data/missing"
+        }
+      }
+    }
+  }
+}

test/data/sources/org.osbuild.ostree/cases/success.json

@@ -0,0 +1,12 @@
+{
+  "expects": "success",
+  "org.osbuild.ostree": {
+    "items": {
+      "d6243b0d0ca3dc2aaef2e0eb3e9f1f4836512c2921007f124b285f7c466464d8": {
+        "remote": {
+          "url": "http://localhost/sources/org.osbuild.ostree/data/repo"
+        }
+      }
+    }
+  }
+}

test/data/sources/org.osbuild.ostree/data/repo/config

@@ -0,0 +1,3 @@
+[core]
+repo_version=1
+mode=archive-z2

test/data/sources/org.osbuild.ostree/data/repo/refs/heads/test/ostree

@@ -0,0 +1 @@
+d6243b0d0ca3dc2aaef2e0eb3e9f1f4836512c2921007f124b285f7c466464d8