Add some notes related to continuous build on Hydra

admin/ChangeLog

+2013-08-10  Xue Fuqiao  <xfq.free@gmail.com>
+
+	* notes/hydra: New file.
+
 2013-08-04  Paul Eggert  <eggert@cs.ucla.edu>
 
 	Fix some minor races in hosts lacking mkostemp (Bug#15015).

admin/notes/hydra

+-*- outline -*-
+
+Copyright (C) 2013 Free Software Foundation, Inc.
+See the end of the file for license conditions.
+
+NOTES FOR EMACS CONTINUOUS BUILD ON HYDRA
+
+A continuous build for Emacs trunk can be found at
+http://hydra.nixos.org/jobset/gnu/emacs-trunk
+
+* It builds (and runs ERT tests) on these platforms:
+i686-cygwin
+i686-freebsd
+i686-linux
+x86_64-darwin
+x86_64-linux
+
+* Mail notifications
+Hydra sends notifications about build breakages in Emacs trunk to
+emacs-buildstatus@gnu.org.
+
+If you want to receive these notifications, please subscribe at
+http://lists.gnu.org/mailman/listinfo/emacs-buildstatus
+
+* The Emacs jobset consists of the following jobs:
+
+** The `tarball' job
+which gets the source tree as input, and is just a `make dist' after
+some autoconf/-make or bootstrap script.
+
+** The `build' job
+which gets the result of the tarball job as input, together with
+system identifier, this job basically does a normal make, make check,
+make install.
+
+** The 'coverage' job
+is now running `make check'.
+
+* Other GNU packages
+For a list of other GNU packages that have a continuous build on
+Hydra, see http://hydra.nixos.org/project/gnu
+
+
+This file is part of GNU Emacs.
+
+GNU Emacs 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 3 of the License, or
+(at your option) any later version.
+
+GNU Emacs 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 GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.