add an "integration" test

I noticed that doing links-update for my linux-home repository didn't
work on an old bash version. Building a test case to reproduce...

You should be able to check out this commit later and run

    make test/docker/xenial

and it's supposed to fail with something like

    /src/src/db.sh: line 194: wait: pid 1771 is not a child of this shell

1 files changed, 89 insertions, 0 deletions

diff --git a/test/integration/test.sh b/test/integration/test.sh
new file mode 100755
index 0000000..3bb481f
--- /dev/null
+++ b/test/integration/test.sh
@@ -0,0 +1,89 @@
+#!/usr/bin/env bash
+
+set -o errexit -o nounset -o pipefail
+shopt -s inherit_errexit 2> /dev/null || true
+shopt -s lastpipe
+
+script_dir="$( dirname -- "${BASH_SOURCE[0]}" )"
+script_dir="$( cd -- "$script_dir" && pwd )"
+readonly script_dir
+script_name="$( basename -- "${BASH_SOURCE[0]}" )"
+readonly script_name
+
+root_dir="$( git -C "$script_dir" rev-parse --show-toplevel )"
+readonly root_dir
+
+src_name='linux-home'
+readonly src_name
+src_url="https://github.com/egor-tensin/$src_name.git"
+readonly src_url
+
+test_root_dir=
+test_src_dir=
+
+new_test() {
+    local test_name=
+    [ "${#FUNCNAME[@]}" -gt 1 ] && test_name="${FUNCNAME[1]}"
+    [ "$#" -gt 0 ] && test_name="$1"
+
+    echo
+    echo ======================================================================
+    echo "New test: $test_name"
+
+    test_root_dir="$( mktemp -d )"
+    # mktemp returns /var/..., which is actually in /private/var/... on macOS.
+    test_root_dir="$( readlink -e -- "$test_root_dir" )"
+    test_src_dir="$test_root_dir/$src_name"
+
+    echo "Root directory: $test_root_dir"
+    echo "Shared directory: $test_src_dir"
+    echo ======================================================================
+
+    git clone -q -- "$src_url" "$test_src_dir"
+    cd -- "$test_src_dir"
+}
+
+call_bin_script() {
+    echo
+    echo -n 'Executing script:'
+
+    printf -- ' %q' "$@" --shared-dir "$test_src_dir" --database "$test_root_dir/links.bin"
+    printf -- '\n'
+
+    echo
+    "$@" --shared-dir "$test_src_dir" --database "$test_root_dir/links.bin"
+}
+
+call_update() {
+    call_bin_script "$root_dir/links-update" "$@"
+}
+
+call_remove() {
+    call_bin_script "$root_dir/links-remove"
+}
+
+call_chmod() {
+    call_bin_script "$root_dir/links-chmod" "$@"
+}
+
+test_my_dotfiles_work() {
+    new_test
+    call_update
+}
+
+show_env() {
+    echo
+    echo ======================================================================
+    echo Environment
+    echo ======================================================================
+
+    bash --version
+}
+
+main() {
+    show_env
+
+    test_my_dotfiles_work
+}
+
+main