Add a deploy script

This script should be run to deploy Wish in production. It _should_ do
everything needed, but currently it is created without being tested, so
no warranties :-)

(There will be no warranties anyway, ever :-))

deploy.sh

@@ -0,0 +1,46 @@
+#!/bin/sh
+
+set -eux
+
+if test "$#" -gt 1; then
+	echo >&2 "Usage: $0 [branch]"
+	exit 2
+fi
+
+# Check that worktree is clean
+if test -n "$(git status --porcelain)"; then
+	echo >&2 "FATAL: Tree not clean, refusing to deploy"
+	echo "Hint: This is current \`git status\`:"
+	git status
+	exit 1
+fi
+
+local branch
+
+if test "$#" -eq 1; then
+	branch="$1"
+else
+	branch=master
+fi
+
+local currentbranch="$(git branch --show-current)"
+
+# If we are not on target branch, switch and run again
+if test "$currentbranch" -ne "$branch"
+	exec /bin/sh -eu "git checkout $branch && exec $0"
+fi
+
+echo "Deploying branch $branch"
+
+### Deploying starts here ###
+
+git pull
+. venv/bin/activate
+pip install -U pip setuptools
+pip install -r requirements.txt
+./manage.py migrate
+./manage.py collectstatic # --noinput?
+systemctl --user restart wish.service
+# TODO: Self-checks? i.e. ./manage.py --check and ./manage.py test?
+echo # Just a blank line 
+echo '=== Deploy successful ==='