libostree: add versioning macros

OSTree currently provides no way to inspect the versioning
information at run time, being only available at compile
time through pkg-config.

This is a problem for e.g. Flatpak, that needs to check
whether the 'update-frequency' option is available. Checking
at compile time isn't great since it's not looking for new
symbols, but only if an optional feature is present.

This commit, then, adds a new header that is generated
at compile time, exposing OSTree's versioning information.

Closes: #728
Approved by: cgwalters

src/libostree/ostree-version.h.in

@@ -0,0 +1,82 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2017 Georges Basile Stavracas Neto <georges.stavracas@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2 of the licence or (at
+ * your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#pragma once
+
+/**
+ * SECTION:ostree-version
+ * @short_description: ostree version checking
+ *
+ * ostree provides macros to check the version of the library
+ * at compile-time
+ */
+
+/**
+ * OSTREE_YEAR_VERSION:
+ *
+ * ostree year version component (e.g. 2017 if %OSTREE_VERSION is 2017.2)
+ */
+#define OSTREE_YEAR_VERSION (@YEAR_VERSION@)
+
+/**
+ * OSTREE_RELEASE_VERSION:
+ *
+ * ostree release version component (e.g. 2 if %OSTREE_VERSION is 2017.2)
+ */
+#define OSTREE_RELEASE_VERSION (@RELEASE_VERSION@)
+
+/**
+ * OSTREE_VERSION
+ *
+ * ostree version.
+ */
+#define OSTREE_VERSION (@VERSION@)
+
+/**
+ * OSTREE_VERSION_S:
+ *
+ * ostree version, encoded as a string, useful for printing and
+ * concatenation.
+ */
+#define OSTREE_VERSION_S "@VERSION@"
+
+#define OSTREE_ENCODE_VERSION(year,release) \
+        ((year) << 16 | (release))
+
+/**
+ * OSTREE_VERSION_HEX:
+ *
+ * ostree version, encoded as an hexadecimal number, useful for
+ * integer comparisons.
+ */
+#define OSTREE_VERSION_HEX \
+        (OSTREE_ENCODE_VERSION (OSTREE_YEAR_VERSION, OSTREE_RELEASE_VERSION))
+
+/**
+ * OSTREE_CHECK_VERSION:
+ * @year: required year version
+ * @release: required release version
+ *
+ * Compile-time version checking. Evaluates to %TRUE if the version
+ * of ostree is equal or greater than the required one.
+ */
+#define OSTREE_CHECK_VERSION(year,release)   \
+        (OSTREE_YEAR_VERSION >= (year) || \
+         (OSTREE_YEAR_VERSION == (year) && OSTREE_RELEASE_VERSION >= (release)))