deltas: Prune deltas when the corresponding "to" commit vanishes

We want prune to actually give you back disk space when using deltas.

src/libostree/ostree-repo-prune.c

@@ -22,6 +22,7 @@
 
 #include "config.h"
 
+#include "ostree-core-private.h"
 #include "ostree-repo-private.h"
 #include "otutil.h"
 
@@ -212,6 +213,49 @@ ostree_repo_prune (OstreeRepo        *self,
                                      cancellable, error))
         goto out;
     }
+
+  { gs_unref_ptrarray GPtrArray *deltas = NULL;
+    guint i;
+
+    if (!ostree_repo_list_static_delta_names (self, &deltas,
+                                              cancellable, error))
+      goto out;
+
+    for (i = 0; i < deltas->len; i++)
+      {
+        const char *deltaname = deltas->pdata[i];
+        const char *dash = strchr (deltaname, '-');
+        const char *to = NULL;
+        gboolean have_commit;
+        gs_free char *from = NULL;
+        gs_free char *deltadir = NULL;
+
+        if (!dash)
+          {
+            to = deltaname;
+          }
+        else
+          {
+            from = g_strndup (deltaname, dash - deltaname);
+            to = dash + 1;
+          }
+
+        if (!ostree_repo_has_object (self, OSTREE_OBJECT_TYPE_COMMIT,
+                                     to, &have_commit,
+                                     cancellable, error))
+          goto out;
+
+        if (have_commit)
+          continue;
+
+        deltadir = _ostree_get_relative_static_delta_path (from, to, NULL);
+
+        if (!gs_shutil_rm_rf_at (self->repo_dir_fd, deltadir,
+                                 cancellable, error))
+          goto out;
+      }
+  }
+
   ret = TRUE;
   *out_objects_total = (data.n_reachable_meta + data.n_unreachable_meta +
                         data.n_reachable_content + data.n_unreachable_content);