image: Move package manifest generator to hook

Now that the package manifest generator is independent of the `/var`
mount, it can be run from an image hook like the flatpak and ostree
manifest generators.

https://phabricator.endlessm.com/T35244

config/defaults.ini

@@ -132,6 +132,7 @@ hooks_add =
   70-flatpak-appstream-catalog
   70-flatpak-manifest
   70-ostree-manifest
+  70-packages-manifest
   80-ldconfig-aux-cache.chroot
 
 # Gzip compression by default (valid choices: gz or xz)

helpers/packages-manifest → hooks/image/70-packages-manifest

@@ -35,5 +35,9 @@ for pkg in sorted(cache):
         'size': pkg.installed.installed_size,
     }
 
-# Print out the json
-print(json.dumps(data, sort_keys=True))
+# Now write out the json to a fragment
+manifestdir = os.environ['EIB_MANIFESTDIR']
+manifest_path = os.path.join(manifestdir, 'packages.json')
+print('Writing packages manifest info to', manifest_path)
+with open(manifest_path, 'w') as manifest:
+    json.dump(data, manifest, sort_keys=True)

stages/eib_image

@@ -161,12 +161,6 @@ dpkgdir="${OSTREE_DEPLOYMENT}"/usr/share/dpkg/database
 packageinfo="${EIB_TMPDIR}"/packages.txt
 dpkg-query -W --admindir="${dpkgdir}" > "${packageinfo}"
 
-# Add package info to manifest using helper. This needs to be run here
-# rather than in an image hook because the dpkg database will be masked
-# by the OS /var mount.
-pkg_manifest="${EIB_MANIFESTDIR}"/packages.json
-"${EIB_HELPERSDIR}"/packages-manifest > "${pkg_manifest}"
-
 run_hooks content "${OSTREE_DEPLOYMENT}"
 
 create_image() {