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diff --git a/include/git2/refdb_backend.h b/include/git2/refdb_backend.h
new file mode 100644
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+++ b/include/git2/refdb_backend.h
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+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_git_refdb_backend_h__
+#define INCLUDE_git_refdb_backend_h__
+
+#include "common.h"
+#include "types.h"
+#include "oid.h"
+
+/**
+ * @file git2/refdb_backend.h
+ * @brief Git custom refs backend functions
+ * @defgroup git_refdb_backend Git custom refs backend API
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/** An instance for a custom backend */
+struct git_refdb_backend {
+    unsigned int version;
+
+	/**
+	 * Queries the refdb backend to determine if the given ref_name
+	 * exists.  A refdb implementation must provide this function.
+	 */
+	int (*exists)(
+		int *exists,
+		struct git_refdb_backend *backend,
+		const char *ref_name);
+
+	/**
+	 * Queries the refdb backend for a given reference.  A refdb
+	 * implementation must provide this function.
+	 */
+	int (*lookup)(
+		git_reference **out,
+		struct git_refdb_backend *backend,
+		const char *ref_name);
+
+	/**
+	 * Enumerates each reference in the refdb.  A refdb implementation must
+	 * provide this function.
+	 */
+	int (*foreach)(
+		struct git_refdb_backend *backend,
+		unsigned int list_flags,
+		git_reference_foreach_cb callback,
+		void *payload);
+
+	/**
+	 * Enumerates each reference in the refdb that matches the given
+	 * glob string.  A refdb implementation may provide this function;
+	 * if it is not provided, foreach will be used and the results filtered
+	 * against the glob.
+	 */
+	int (*foreach_glob)(
+		struct git_refdb_backend *backend,
+		const char *glob,
+		unsigned int list_flags,
+		git_reference_foreach_cb callback,
+		void *payload);
+
+	/**
+	 * Writes the given reference to the refdb.  A refdb implementation
+	 * must provide this function.
+	 */
+	int (*write)(struct git_refdb_backend *backend, const git_reference *ref);
+
+	/**
+	 * Deletes the given reference from the refdb.  A refdb implementation
+	 * must provide this function.
+	 */
+	int (*delete)(struct git_refdb_backend *backend, const git_reference *ref);
+
+	/**
+	 * Suggests that the given refdb compress or optimize its references.
+	 * This mechanism is implementation specific.  (For on-disk reference
+	 * databases, this may pack all loose references.)    A refdb
+	 * implementation may provide this function; if it is not provided,
+	 * nothing will be done.
+	 */
+	int (*compress)(struct git_refdb_backend *backend);
+
+	/**
+	 * Frees any resources held by the refdb.  A refdb implementation may
+	 * provide this function; if it is not provided, nothing will be done.
+	 */
+	void (*free)(struct git_refdb_backend *backend);
+};
+
+#define GIT_ODB_BACKEND_VERSION 1
+#define GIT_ODB_BACKEND_INIT {GIT_ODB_BACKEND_VERSION}
+
+/**
+ * Constructors for default refdb backends.
+ */
+GIT_EXTERN(int) git_refdb_backend_fs(
+	struct git_refdb_backend **backend_out,
+	git_repository *repo,
+	git_refdb *refdb);
+
+GIT_END_DECL
+
+#endif