golang: Add note about difficulty of parsing go version numbers.

golang/config-test.go

@@ -1,5 +1,34 @@
+/* libguestfs Go configuration test
+ * Copyright (C) 2013 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/* This is called from ./configure to check that golang works
+ * and is above the minimum required version.
+ */
+
 package main
 
 func main() {
-	/* XXX Check for minimum runtime.Version() >= 1.1.1 */
+	/* XXX Check for minimum runtime.Version() >= "go1.1.1"
+         * Unfortunately go version numbers are not easy to parse.
+         * They have the 3 formats "goX.Y.Z", "release.rN" or
+         * "weekly.YYYY-MM-DD".  The latter two formats are mostly
+         * useless, and the first one is hard to parse.  See also
+         * cmpGoVersion in
+         * http://web.archive.org/web/20130402235148/http://golang.org/src/cmd/go/get.go?m=text
+         */
 }