scripts: time-machine: Error when attempting to visit too old commits.

* doc/guix.texi (Invoking guix time-machine): Document limitation.
* guix/inferior.scm (cached-channel-instance): New VALIDATE-CHANNELS
argument.  Use it to validate channels when there are no cache hit.
* guix/scripts/time-machine.scm
(%options): Tag the given reference with 'tag-or-commit instead of 'commit.
(%oldest-possible-commit): New variable.
(guix-time-machine) <validate-guix-channel>: New nested procedure.  Pass it to
the 'cached-channel-instance' call.
* tests/guix-time-machine.sh: New test.
* Makefile.am (SH_TESTS): Register it.

Suggested-by: Simon Tournier <zimon.toutoune@gmail.com>
Reviewed-by: Ludovic Courtès <ludo@gnu.org>
Reviewed-by: Simon Tournier <zimon.toutoune@gmail.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/guix-time-machine.sh b/tests/guix-time-machine.sh
new file mode 100644
index 0000000000..8b62ef75ea
--- /dev/null
+++ b/tests/guix-time-machine.sh
@@ -0,0 +1,28 @@
+# GNU Guix --- Functional package management for GNU
+# Copyright © 2023 Maxim Cournoyer <maxim.cournoyer@gmail.com>
+#
+# This file is part of GNU Guix.
+#
+# GNU Guix 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 Guix 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 Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+#
+# Test the 'guix time-machine' command-line utility.
+#
+
+guix time-machine --version
+
+# Visiting a commit older than v1.0.0 fails.
+! guix time-machine --commit=v0.15.0
+
+exit 0