I use Emacs as my primary text editor and I use it to edit commit messages for Git. I almost never use the -m option with git commit. Since I have a fairly customised Emacs configuration based around Sam Aaron’s Emacs Live, this means that for every commit, there is a visible delay for Emacs to start up for the commit message. I was looking for ways to reduce this and figured out that running Emacs in daemon mode and using emacsclient as the GIT_EDITOR would solve this.

Running an Emacs daemon at start up on Mac OS X

The recommended way of running an application at start up on Mac OS X is to use launchd. Launchd configurations are written as XML files created in ~/Library/LaunchAgents or /Library/LaunchAgents depending on whether the app needs to be run for the current user or for all users. Here is the plist file for Emacs at ~/Library/LaunchAgents/gnu.emacs.daemon.plist, taken from EmacsWiki:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
"http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>gnu.emacs.daemon</string>
    <key>ProgramArguments</key>
    <array>
      <string>/Applications/Emacs.app/Contents/MacOS/Emacs</string>
      <string>--daemon</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
    <key>ServiceDescription</key>
    <string>Gnu Emacs Daemon</string>
    <key>UserName</key>
    <string>YOUR USER NAME</string>
  </dict>
</plist>

This is loaded by running

sudo launchctl load -w ~/Library/LaunchAgents/gnu.emacs.daemon.plist

Using Emacs client as the editor

This is done by adding

export EDITOR="/Applications/Emacs.app/Contents/MacOS/bin/emacsclient"
export GIT_EDITOR="/Applications/Emacs.app/Contents/MacOS/bin/emacsclient"

to .zshrc or .bashrc.

This setup significantly reduces the Emacs startup time while committing changes.