Add xbps_get_pkg_revision() to get the revision string.

--HG--
extra : convert_revision : 5c58a44db6b3f1ff2c7f75173aff7d6509dfd4c9

include/xbps_api.h

@@ -150,6 +150,7 @@ bool		xbps_check_is_installed_pkgname(const char *);
 char *		xbps_get_pkg_index_plist(const char *);
 char *		xbps_get_pkg_name(const char *);
 const char *	xbps_get_pkg_version(const char *);
+const char *	xbps_get_pkg_revision(const char *);
 bool		xbps_pkg_has_rundeps(prop_dictionary_t);
 void		xbps_set_rootdir(const char *);
 const char *	xbps_get_rootdir(void);

lib/util.c

@@ -171,6 +171,21 @@ xbps_get_pkg_version(const char *pkg)
 	return tmp + 1; /* skip first '-' */
 }
 
+const char *
+xbps_get_pkg_revision(const char *pkg)
+{
+	const char *tmp;
+
+	assert(pkg != NULL);
+
+	/* Get the required revision */
+	tmp = strrchr(pkg, '_');
+	if (tmp == NULL)
+		return NULL;
+
+	return tmp + 1; /* skip first '_' */
+}
+
 char *
 xbps_get_pkg_name(const char *pkg)
 {