I wrote about my efforts to automate my publishing workflow a couple of weeks ago, (egad!) and I wanted to follow that up with a somewhat more useful elucidation of how all of the gears work around here.

At first I had this horrible scheme setup that dependent on regular builds triggered by cron, which is a functional, if inelegant solution. There's a lot of tasks that you can give the appearance of "real time," responsiveness by scheduling more brute tasks regularly enough. The truth is, however, that its not quite the same, and I knew that there was a better way.

Basically the "right way" to solve this problem is to use the "hooks" provided by the git repositories that I use to store the source of the website. Hooks, in this context refer to a number of scripts which are optionally run before or after various operations in the repositories that allow you to attach actions to the operations you perform on your git repositories. In effect, you can say "when I git push do these other things" or "before I git commit check for these conditions, and if they're not met, reject the commit" and so forth. The possibilities can be a bit staggering.

In this case what happen is: I commit to the tychoish.com repositories a script that synchronizes the appropriate local packages runs and publishes changes to the server. It then sends me an xmpp message saying that this operation is in progress. This runs as the post-commit hook, and for smaller sites could simply be "git push origin master". Because tychoish is a large site, and I don't want to be rebuilding it constantly, I do the following:


# This script is meant to be run in a cron job to perform a rebuilding
# of the slim contents of a jekyll site.
# This script can be run several times an hour to greatly simplify the
# publishing routine of a jekyll site.

cd ~/sites/tychoish.com/

# Saving and Fetching Remote Updates from tychoish.com
git pull >/dev/null &&

# Local Adding and Committing
git checkout master >/dev/null 2>&1
git add .
git commit -a -q -m "$HOSTNAME: changes prior to an  slim rebuild"  >/dev/null 2>

# Local "full-build" Branch Mangling
git checkout full-build >/dev/null 2>&1 &&
git merge master &&

# Local "slim-bild" Branch Magling and Publishing
git checkout slim-build >/dev/null 2>&1 &&
git merge master &&
git checkout master >/dev/null 2>&1 &
git push --all

# echo done

Then on the server, once the copy of the repo on the server is current with the changes published to it (i.e. the post-update hook), the following code is run:

# An example hook script to prepare a packed repository for use over
# dumb transports.
# To enable this hook, make this file executable by "chmod +x post-update".

unset GIT_DIR

export GIT_DIR

cd /path/to/build/tychoish.com
git pull origin;

/path/to/scripts/jekyll-rebuild-tychoish-auto-slim &


When the post-update hook runs, in runs in the context of the repository that you just pushed to, and unless you do the magic (technical term, it seems) the GIT_DIR and GIT_WORKING_TREE variables are stuck in the environment and the commands you run fail. So basically this is a fancy git pull, in a third repository (the one that the site is built from.) The script jekyll-rebuild-tychoish-auto-slim looks like this:

# to be run on the server

# setting the variables

 cd ${SRCDIR}
 git checkout ${BUILDTYPE}-build >/dev/null 2>&1
 git pull source >/dev/null 2>&1

 /var/lib/gems/1.8/bin/jekyll ${SRCDIR} ${DSTDIR} >/dev/null 2>&1
 echo \<jekyll\> completed \*${BUILDTYPE}\* build of ${SITENAME} | xmppipe garen@tychoish.com

 git checkout ${DEFAULTBUILD}-build >/dev/null 2>&1


This sends me an xmpp message when the build has completed. And does the needful site rebuilding. The xmppipe command I use is really the following script:

# pipes standard in to an xmpp message, sent to the JIDs on the commandline
# usage: bash$ `echo "message body" | xmppipe garen@tychoish.com
# code shamelessly stolen from:
# http://stackoverflow.com/questions/170503/commandline-jabber-client/170564#170564

use strict;
use warnings;

use Net::Jabber qw(Client);

my $server = "tychoish.com";
my $port = "5222";
my $username = "bot";
my $password = ";
my $resource = "xmppipe";
my @recipients = @ARGV;

my $clnt = new Net::Jabber::Client;

my $status = $clnt->Connect(hostname=>$server, port=>$port);

if (!defined($status)) {
  die "Jabber connect error ($!)\n";
my @result = $clnt->AuthSend(username=>$username,

if ($result[0] ne "ok") {
  die "Jabber auth error: @result\n";

my $body = '';
while (<STDIN>) {
  $body .= $_;

foreach my $to (@recipients) {


Mark the above as executable and put it in your path somewhere. You'll want to install the Net::Jabber Perl module, if you haven't already.

The one final note. If you're using a tool like gitosis to manage your git repositories, all of the hooks will be executed by the gitosis user. This means that this user will need to have write access the "build" copy of the repository and the public directory as well. You may be able to finesse this with the +s "switch uid" bit, or some clever use of the gitosis user group.

The End.