Port to Tracker 3

Mostly the port is straightforward, we connect to tracker-miner-fs
explicitly over D-Bus instead of the centralized tracker-store daemon
we connected to previously.

The search-engine-tracker test is now isolated from the user's real
Tracker index using the `tracker-sandbox` script provided by Tracker,
and it lets tracker-miner-fs index the test file rather than trying
to synthesize the expected database contents.

There are more changes in nautilus-tag-manager.c.  Until now, starred
file information was stored in the tracker-miner-fs database. This has
some downsides, firstly the data is deleted if someone runs `tracker
reset --hard`, secondly it isn't possible to do this from inside a
Flatpak sandbox with Tracker 3.0.  because the

This commit changes the NautilusTagManager to set up a private
database inside XDG_DATA_HOME/nautilus/tags. This stores the starred
file information. The database is managed with Tracker, which allows us
to continue using the rename-tracking that tracker-miner-fs provides.
The same limitations apply as before that only files in indexed
locations can be starred.

4 files changed, 38 insertions, 0 deletions

diff --git a/data/meson.build b/data/meson.build
index 7218b84e0..e51ed50b1 100644
--- a/data/meson.build
+++ b/data/meson.build
@@ -137,3 +137,5 @@ if appstream_util.found()
     ]
   )
 endif
+
+subdir('ontology')
diff --git a/data/ontology/meson.build b/data/ontology/meson.build
new file mode 100644
index 000000000..cb80e86a1
--- /dev/null
+++ b/data/ontology/meson.build
@@ -0,0 +1,8 @@
+ontology_data = files(
+  'nautilus.description',
+  'nautilus.ontology',
+)
+
+install_data(ontology_data,
+  install_dir: join_paths(datadir, 'nautilus', 'ontology')
+)
diff --git a/data/ontology/nautilus.description b/data/ontology/nautilus.description
new file mode 100644
index 000000000..42f4102c3
--- /dev/null
+++ b/data/ontology/nautilus.description
@@ -0,0 +1,9 @@
+@prefix dsc: <http://tracker.api.gnome.org/ontology/v3/dsc#> .
+
+<virtual-ontology-uri:nautilus.ontology> a dsc:Ontology ;
+    dsc:title "Nautilus ontology" ;
+    dsc:description "Tracker database schema for Nautilus private data." ;
+
+    dsc:localPrefix "nautilus" ;
+    dsc:baseUrl "https://gitlab.gnome.org/GNOME/nautilus#" ;
+    dsc:relativePath "./nautilus.ontology" ;
diff --git a/data/ontology/nautilus.ontology b/data/ontology/nautilus.ontology
new file mode 100644
index 000000000..ed56df447
--- /dev/null
+++ b/data/ontology/nautilus.ontology
@@ -0,0 +1,19 @@
+@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
+@prefix nrl: <http://tracker.api.gnome.org/ontology/v3/nrl#> .
+@prefix nautilus: <https://gitlab.gnome.org/GNOME/nautilus#> .
+
+nautilus: a nrl:Namespace, nrl:Ontology ;
+    nrl:prefix "nautilus" ;
+    nrl:lastModified "2020-05-01T10:00:00Z" .
+
+nautilus:FileReference a rdfs:Class ;
+    rdfs:comment "A unique ID for a file, corresponding with the nie:InformationElement created by tracker-miner-fs. We use a unique ID rather than the file URL so the star will follow renames." ;
+    rdfs:subClassOf rdfs:Resource .
+
+nautilus:starred a rdf:Property ;
+    rdfs:comment "Marks resources that are starred in Nautilus." ;
+    rdfs:domain nautilus:FileReference ;
+    rdfs:range xsd:boolean ;
+    nrl:maxCardinality 1 .