pack: Add test for '--relocatable'.

* tests/guix-pack-relocatable.sh: New file.
* Makefile.am (SH_TESTS): Add it.

Makefile.am

@@ -406,6 +406,7 @@ SH_TESTS =					\
   tests/guix-gc.sh				\
   tests/guix-hash.sh				\
   tests/guix-pack.sh				\
+  tests/guix-pack-relocatable.sh		\
   tests/guix-package.sh				\
   tests/guix-package-net.sh			\
   tests/guix-system.sh				\

tests/guix-pack-relocatable.sh

@@ -0,0 +1,61 @@
+# GNU Guix --- Functional package management for GNU
+# Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
+#
+# 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 pack --relocatable' using the external store, if any.
+#
+
+guix pack --version
+
+# 'guix pack --relocatable' requires a C compiler and libc.a, which our
+# bootstrap binaries don't provide.  To make the test relatively inexpensive,
+# run it on the user's global store if possible, on the grounds that binaries
+# may already be there or can be built or downloaded inexpensively.
+
+NIX_STORE_DIR="`guile -c '(use-modules (guix config))(display %storedir)'`"
+localstatedir="`guile -c '(use-modules (guix config))(display %localstatedir)'`"
+GUIX_DAEMON_SOCKET="$localstatedir/guix/daemon-socket/socket"
+export NIX_STORE_DIR GUIX_DAEMON_SOCKET
+
+if ! guile -c '(use-modules (guix)) (exit (false-if-exception (open-connection)))'
+then
+    exit 77
+fi
+
+STORE_PARENT="`dirname $NIX_STORE_DIR`"
+export STORE_PARENT
+if test "$STORE_PARENT" = "/"; then exit 77; fi
+
+# This test requires user namespaces and associated command-line tools.
+if ! unshare -mrf sh -c 'mount -t tmpfs none "$STORE_PARENT"'
+then
+    exit 77
+fi
+
+test_directory="`mktemp -d`"
+export test_directory
+trap 'chmod -Rf +w "$test_directory"; rm -rf "$test_directory"' EXIT
+
+tarball="`guix pack -R -S /Bin=bin sed`"
+(cd "$test_directory"; tar xvf "$tarball")
+
+# Run that relocatable 'sed' in a user namespace where we "erase" the store by
+# mounting an empty file system on top of it.  That way, we exercise the
+# wrapper code that creates the user namespace and bind-mounts the store.
+unshare -mrf sh -c 'mount -t tmpfs none "$STORE_PARENT"; echo "$STORE_PARENT"/*; "$test_directory/Bin/sed" --version > "$test_directory/output"'
+grep 'GNU sed' "$test_directory/output"