admin/switch: New builtin to switch between trees

This is something I want to make easier, as it better showcases the
flexibility of OSTree.

tests/libtest.sh

@@ -226,6 +226,13 @@ EOF
     echo "a new executable" > usr/bin/sh
     ostree --repo=${test_tmpdir}/testos-repo commit -b testos/buildmaster/x86_64-runtime -s "Build"
 
+    cd ${test_tmpdir}
+    cp -a osdata osdata-devel
+    cd osdata-devel
+    mkdir -p usr/include
+    echo "a development header" > usr/include/foo.h
+    ostree --repo=${test_tmpdir}/testos-repo commit -b testos/buildmaster/x86_64-devel -s "Build"
+
     ostree --repo=${test_tmpdir}/testos-repo fsck -q
 
     cd ${test_tmpdir}

tests/test-admin-deploy-switch.sh

@@ -0,0 +1,44 @@
+#!/bin/bash
+#
+# Copyright (C) 2011,2014 Colin Walters <walters@verbum.org>
+#
+# This library 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 License, 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.
+
+set -e
+
+. $(dirname $0)/libtest.sh
+
+echo "1..1"
+
+setup_os_repository "archive-z2" "syslinux"
+
+echo "ok setup"
+
+echo "1..2"
+
+ostree --repo=sysroot/ostree/repo remote add --set=gpg-verify=false testos file://$(pwd)/testos-repo
+ostree --repo=sysroot/ostree/repo pull testos testos/buildmaster/x86_64-runtime
+ostree admin --sysroot=sysroot deploy --karg=root=LABEL=MOO --karg=quiet --os=testos testos:testos/buildmaster/x86_64-runtime
+assert_not_has_file sysroot/ostree/deploy/testos/current/usr/include/foo.h
+if ostree admin --sysroot=sysroot switch --os=testos testos/buildmaster/x86_64-runtime; then
+    assert_not_reached "Switch to same ref unexpectedly succeeded"
+fi
+echo "ok switch expected error"
+
+ostree admin --sysroot=sysroot switch --os=testos testos/buildmaster/x86_64-devel
+assert_file_has_content sysroot/ostree/deploy/testos/current/usr/include/foo.h 'header'
+
+echo "ok switch"