start of deployment script

deploy.conf

key /path/to/whatever.pem
user deployer-of-doom
addr n.n.n.n
repo git@github.com:visionmedia/express.git
path /path/to/www/whatever
branch origin/master
command /path/to/www/whatever/restart

deploy.sh

#!/usr/bin/env bash

VERSION="0.0.1"
CONFIG=./deploy.conf
LOG=/tmp/deploy.log
ENV=
WD=.

#
# Output usage information.
#

usage() {
  cat <<-EOF

  Usage: deploy [options] <env> [command]

  Options:

    -C, --chdir <path>   change the working directory to <path>
    -c, --config <path>  set config path defaults to ./deploy.conf
    -V, --version        output program version
    -h, --help           output help information

  Commands:

    setup                run remote setup commands
    deploy [rev]         deploy to [rev] or HEAD
    revert [n]           revert to [n]th last deployment or 1
    config [key]         output config file or [key]
    curr[ent]            output current release commit
    prev[ious]           output previous release commit
    exec|run <cmd>       execute the given <cmd>
    list                 list previous deploy commits

EOF
}

#
# Abort with <msg>
#

abort() {
  echo
  echo "  $@" 1>&2
  echo
  exit 1
}

#
# Log <msg>.
#

log() {
  echo "... $@"
}

#
# Set configuration file <path>.
#

set_config_path() {
  test -f $1 || abort 'invalid --config path'
  CONFIG=$1
}

#
# Check if config <section> exists.
#

config_section() {
  grep "^\[$1" $CONFIG &> /dev/null
}

#
# Get config value by <key>.
#

config_get() {
  local key=$1
  test -n "$key" \
    && grep "^\[$ENV" -A 20 $CONFIG \
    | grep "^$key" \
    | head -n 1 \
    | cut -d ' ' -f 2
}

#
# Output version.
#

version() {
  echo $VERSION
}

#
# Run the given remote <cmd>.
#

run() {
  local url="`config_get user`@`config_get addr`"
  local key=`config_get key`
  if test -n "$key"; then
    local shell="ssh -i $key $url"
  else
    local shell="ssh $url"
  fi
  echo $shell $@ >> $LOG
  $shell $@
}

#
# Output config or [key].
#

config() {
  if test $# -eq 0; then
    cat $CONFIG
  else
    config_get $1
  fi
}

#
# Run setup.
#

setup() {
  local path=`config_get path`
  local repo=`config_get repo`
  local branch=`config_get branch`
  run "mkdir -p $path/{shared/{logs,pids},source}"
  log running setup
  log cloning $repo
  run "git clone $repo $path/source"
  log setup complete
}

#
# Deploy <ref>.
#

deploy() {
  local ref=$1
  local path=`config_get path`
  log deploying $ref

  # fetch source
  run "cd $path/source && git fetch origin && git reset --hard $ref"

  # link current
  run "ln -sf $path/source $path/current"

  # deploy log
  run "cd $path/source && \
      echo \`git rev-parse --short HEAD\` \
      >> $path/.deploys"

  # command
  local cmd=`config_get command`
  if test -n "$cmd"; then
    log "executing $ $cmd"
    run "cd $path/current && $cmd"
  fi

  # done
  log deploy complete
}

#
# Get current commit.
#

current_commit() {
  local path=`config_get path`
  run "cd $path/source && \
      git rev-parse --short HEAD"
}

#
# Get <n>th deploy commit.
#

nth_deploy_commit() {
  local n=$1
  local path=`config_get path`
  run "cat $path/.deploys | tail -n $n | head -n 1 | cut -d ' ' -f 1"
}

#
# List deploys.
#

list_deploys() {
  local path=`config_get path`
  run "cat $path/.deploys"
}

#
# Revert to the <n>th last deployment.
#

revert_to() {
  local n=$1
  log "reverting $((n - 1)) deploy(s)"
  local commit=`nth_deploy_commit $n`
  deploy $commit
}

#
# Require environment arg.
#

require_env() {
  config_section $ENV || abort "[$ENV] config section not defined"
  test -z "$ENV" && abort "<env> required"
}

# parse argv

while test $# -ne 0; do
  arg=$1; shift
  case $arg in
    -h|--help) usage; exit ;;
    -V|--version) version; exit ;;
    -c|--config) set_config_path $1 ;;
    -C|--chdir) WD=$1; CONFIG=$WD/deploy.conf ;;
    run|exec) require_env; run "cd `config_get path` && $@"; exit ;;
    curr|current) require_env; current_commit; exit ;;
    prev|previous) require_env; nth_deploy_commit 2; exit ;;
    revert) require_env; revert_to ${1-2}; exit ;;
    setup) require_env; setup $@; exit ;;
    list) require_env; list_deploys; exit ;;
    config) config $@; exit ;;
    *) ENV=$arg ;;
  esac
done

require_env

# chdir
test "$WD" != "." && cd $WD && log cd $WD

# deploy
deploy `config_get branch`

haha thanks man