Sign on the Dotted Line

I use Emacs for all my Django/YUI server work, and all that work is stored in Bazaar repositories. Emacs has a great, modular mode for interacting with a variety of version control systems, called VC.

VC can handle pretty much the full range of dealing with files and directories under version control: finding out which files have changed (bzr st), what changed in those files (bzr diff), and committing those changes to the repository (bzr ci). However, for some of our projects, we sign our commit messages with GnuPG. To date, this required running from the command line for these particular projects. I wanted to remain in the flow inside Emacs, but it seemed unable to accommodate this added step.

So, I did some investigating. At first, I thought all I’d need would be gnupg-agent.

    $ sudo apt-get install gnupg-agent

In my ~/.gnupg/gpg.conf, I added (well, uncommented):

    use-agent

In my ~/.gnupg/gpg-agent.conf, I added:

    pinentry-program /usr/bin/pinentry-gtk-2
    default-cache-ttl 86400
    max-cache-ttl 86400

And I start up gpg-agent with every login by adding this line to my ~/.xsession file:

    eval $(gpg-agent --daemon)

However, this alone wasn’t enough to get VC to recognize that it should defer to a running agent for signing the commits. And I could find no way to specify additional command line arguments for the gpg_signing_command in my ~/.bazaar/bazaar.conf file, like so:

    [DEFAULT]
    launchpad_username = urbanape
    email = {my work email}
    gpg_signing_command = /home/zbir/bin/vc-bzr-gpg

So instead, I wrote a script at ~/bin/vc-bzr-gpg that would internalize those additional arguments:

    #!/bin/sh

    /usr/bin/gpg --verbose --use-agent --no-tty $@

Made it executable, and voilà! Commits made in VC mode are signed by the agent (and I’m prompted for my passphrase if the agent isn’t running or hasn’t been authorized within the cache-ttl in my gpg-agent.conf).

Now, if there was only a way to push to Launchpad and submit branches for review from within Emacs…