lib/refs: Add methods for setting/listing collection–refs

These are tuples of (collection ID, ref name) which are a globally-unique
form of local ref. They use OstreeCollectionRef as an identifier, and hence
need to be accessed using new API, as the existing API uses string
identifiers and sometimes accepts refspecs. Remote names are not
supported as part an OstreeCollectionRef.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Closes: #924
Approved by: cgwalters

src/libostree/ostree-repo-commit.c

@@ -1347,6 +1347,11 @@ ensure_txn_refs (OstreeRepo *self)
 {
   if (self->txn_refs == NULL)
     self->txn_refs = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_free);
+  if (self->txn_collection_refs == NULL)
+    self->txn_collection_refs = g_hash_table_new_full (ostree_collection_ref_hash,
+                                                       ostree_collection_ref_equal,
+                                                       (GDestroyNotify) ostree_collection_ref_free,
+                                                       g_free);
 }
 
 /**
@@ -1410,6 +1415,41 @@ ostree_repo_transaction_set_ref (OstreeRepo *self,
   g_hash_table_replace (self->txn_refs, refspec, g_strdup (checksum));
 }
 
+/**
+ * ostree_repo_transaction_set_collection_ref:
+ * @self: An #OstreeRepo
+ * @ref: The collection–ref to write
+ * @checksum: (nullable): The checksum to point it to
+ *
+ * If @checksum is not %NULL, then record it as the target of local ref named
+ * @ref.
+ *
+ * Otherwise, if @checksum is %NULL, then record that the ref should
+ * be deleted.
+ *
+ * The change will not be written out immediately, but when the transaction
+ * is completed with ostree_repo_commit_transaction(). If the transaction
+ * is instead aborted with ostree_repo_abort_transaction(), no changes will
+ * be made to the repository.
+ *
+ * Since: 2017.8
+ */
+void
+ostree_repo_transaction_set_collection_ref (OstreeRepo                *self,
+                                            const OstreeCollectionRef *ref,
+                                            const char                *checksum)
+{
+  g_return_if_fail (OSTREE_IS_REPO (self));
+  g_return_if_fail (self->in_transaction == TRUE);
+  g_return_if_fail (ref != NULL);
+  g_return_if_fail (checksum == NULL || ostree_validate_checksum_string (checksum, NULL));
+
+  ensure_txn_refs (self);
+
+  g_hash_table_replace (self->txn_collection_refs,
+                        ostree_collection_ref_dup (ref), g_strdup (checksum));
+}
+
 /**
  * ostree_repo_set_ref_immediate:
  * @self: An #OstreeRepo
@@ -1431,7 +1471,40 @@ ostree_repo_set_ref_immediate (OstreeRepo *self,
                                GCancellable  *cancellable,
                                GError       **error)
 {
-  return _ostree_repo_write_ref (self, remote, ref, checksum,
+  const OstreeCollectionRef _ref = { NULL, (gchar *) ref };
+  return _ostree_repo_write_ref (self, remote, &_ref, checksum,
+                                 cancellable, error);
+}
+
+/**
+ * ostree_repo_set_collection_ref_immediate:
+ * @self: An #OstreeRepo
+ * @ref: The collection–ref to write
+ * @checksum: (nullable): The checksum to point it to, or %NULL to unset
+ * @cancellable: GCancellable
+ * @error: GError
+ *
+ * This is like ostree_repo_transaction_set_collection_ref(), except it may be
+ * invoked outside of a transaction.  This is presently safe for the
+ * case where we're creating or overwriting an existing ref.
+ *
+ * Returns: %TRUE on success, %FALSE otherwise
+ * Since: 2017.8
+ */
+gboolean
+ostree_repo_set_collection_ref_immediate (OstreeRepo                 *self,
+                                          const OstreeCollectionRef  *ref,
+                                          const char                 *checksum,
+                                          GCancellable               *cancellable,
+                                          GError                    **error)
+{
+  g_return_val_if_fail (OSTREE_IS_REPO (self), FALSE);
+  g_return_val_if_fail (ref != NULL, FALSE);
+  g_return_val_if_fail (checksum == NULL || ostree_validate_checksum_string (checksum, NULL), FALSE);
+  g_return_val_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable), FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+  return _ostree_repo_write_ref (self, NULL, ref, checksum,
                                  cancellable, error);
 }
 
@@ -1481,6 +1554,11 @@ ostree_repo_commit_transaction (OstreeRepo                  *self,
       return FALSE;
   g_clear_pointer (&self->txn_refs, g_hash_table_destroy);
 
+  if (self->txn_collection_refs)
+    if (!_ostree_repo_update_collection_refs (self, self->txn_collection_refs, cancellable, error))
+      return FALSE;
+  g_clear_pointer (&self->txn_collection_refs, g_hash_table_destroy);
+
   if (self->commit_stagedir_fd != -1)
     {
       (void) close (self->commit_stagedir_fd);
@@ -1518,6 +1596,7 @@ ostree_repo_abort_transaction (OstreeRepo     *self,
     g_hash_table_remove_all (self->loose_object_devino_hash);
 
   g_clear_pointer (&self->txn_refs, g_hash_table_destroy);
+  g_clear_pointer (&self->txn_collection_refs, g_hash_table_destroy);
 
   if (self->commit_stagedir_fd != -1)
     {