Gracefully shutdown services in Docker container

The problem is `docker stop` only sends SIGTERM to the PID 1 inside the
container, and the PID 1 (`/bin/sh -c ...`) does not take care of
signals. Hence the services (e.g., postgresql, redis, sidekiq, etc)
never have chances to graceful shutdown. Docker just kills the container
after its 10 seconds timeout by default.

What this commit does:

1) Add a wrapper as the default executable of Docker container. Which
   starts services through `runit`, reconfigure Gitlab by `gitlab-ctl`
   and gracefully shutdown all services when a SIGTERM is received.
2) Create an `assets` directory for assets.
3) Add `.dockerignore` file.

Now you'll see the following log messages after `docker stop`:
```
SIGTERM signal received, try to gracefully shutdown all services...
ok: down: logrotate: 1s, normally up
ok: down: nginx: 0s, normally up
ok: down: postgresql: 1s, normally up
ok: down: redis: 0s, normally up
ok: down: sidekiq: 0s, normally up
ok: down: unicorn: 0s, normally up
```

Signed-off-by: kfei <kfei@kfei.net>

2 files changed, 54 insertions, 0 deletions

diff --git a/docker/assets/gitlab.rb b/docker/assets/gitlab.rb
new file mode 100644
index 00000000000..7fddf309c01
--- /dev/null
+++ b/docker/assets/gitlab.rb
@@ -0,0 +1,37 @@
+# External URL should be your Docker instance.
+# By default, this example is the "standard" boot2docker IP.
+# Always use port 80 here to force the internal nginx to bind port 80,
+# even if you intend to use another port in Docker.
+external_url "http://192.168.59.103/"
+
+# Prevent Postgres from trying to allocate 25% of total memory
+postgresql['shared_buffers'] = '1MB'
+
+# Configure GitLab to redirect PostgreSQL logs to the data volume
+postgresql['log_directory'] = '/var/log/gitlab/postgresql'
+
+# Some configuration of GitLab
+# You can find more at https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/README.md#configuration
+gitlab_rails['gitlab_email_from'] = 'gitlab@example.com'
+gitlab_rails['gitlab_support_email'] = 'support@example.com'
+gitlab_rails['time_zone'] = 'Europe/Paris'
+
+# SMTP settings
+# You must use an external server, the Docker container does not install an SMTP server
+gitlab_rails['smtp_enable'] = true
+gitlab_rails['smtp_address'] = "smtp.example.com"
+gitlab_rails['smtp_port'] = 587
+gitlab_rails['smtp_user_name'] = "user"
+gitlab_rails['smtp_password'] = "password"
+gitlab_rails['smtp_domain'] = "example.com"
+gitlab_rails['smtp_authentication'] = "plain"
+gitlab_rails['smtp_enable_starttls_auto'] = true
+
+# Enable LDAP authentication
+# gitlab_rails['ldap_enabled'] = true
+# gitlab_rails['ldap_host'] = 'ldap.example.com'
+# gitlab_rails['ldap_port'] = 389
+# gitlab_rails['ldap_method'] = 'plain' # 'ssl' or 'plain'
+# gitlab_rails['ldap_allow_username_or_email_login'] = false
+# gitlab_rails['ldap_uid'] = 'uid'
+# gitlab_rails['ldap_base'] = 'ou=users,dc=example,dc=com'
diff --git a/docker/assets/wrapper b/docker/assets/wrapper
new file mode 100755
index 00000000000..9e6e7a05903
--- /dev/null
+++ b/docker/assets/wrapper
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+function sigterm_handler() {
+    echo "SIGTERM signal received, try to gracefully shutdown all services..."
+    gitlab-ctl stop
+}
+
+trap "sigterm_handler; exit" TERM
+
+function entrypoint() {
+    # Default is to run runit and reconfigure GitLab
+    gitlab-ctl reconfigure &
+    /opt/gitlab/embedded/bin/runsvdir-start &
+    wait
+}
+
+entrypoint