builder-manifest: Run appstream-compose with no-partial-urls argument

When 0.16.3 is available

This is an alternative to #576

We check at runtime instead of build-time and downgrade instead of
erroring. Checking at build time is insufficient as there is no
guarantee flatpak-builder is run with the same appstream version it
was compiled with.

Ideally we want to compose with `--no-partial-urls` so a warning is
printed if it is not found.

`--no-partial-urls` makes the mirrored URLs in appstream catalogue
data the full URL. So if
`--mirror-screenshot-url=https://example.org/media` and the metainfo
has
`<screenshot><image>https://github.com/foobar.png</image></screenshot>`

After composing with `--no-partial-urls`, it will become
<screenshot><image>https://example.org/media/foobar.png</image></screenshot>`
instead of `/media/foobar.png`.

This is needed by Flathub and generally should be a standard
requirement for any software store (to have a full working URL
instead of a partial whatever-that-is).

Author: bbhtt

src/builder-manifest.c

@@ -3056,9 +3056,16 @@ builder_manifest_cleanup (BuilderManifest *self,
               g_autofree char *arg_media_dir =  g_strdup_printf ("--media-dir=%s",
                                                                  flatpak_file_get_path_cached (media_dir));
 
+              gboolean has_no_partial_urls = appstream_version_check (0, 16, 3);
+              if (!has_no_partial_urls)
+                {
+                  g_warning ("Found AppStream version < 0.16.3. Failed to add '--no-partial-urls' to compose");
+                }
+
               g_print ("Running appstreamcli compose\n");
               g_print ("Saving screenshots in %s\n", flatpak_file_get_path_cached (media_dir));
               if (!appstreamcli_compose (error,
+                                         has_no_partial_urls ? "--no-partial-urls" : NULL,
                                          "--prefix=/",
                                          origin,
                                          arg_base_url,