D E C
22
2008

svn diff and vim

Now that I’m starting to really get used to using svn for all my config files and web dev work, I’ve noticed I use the command svn diff a lot. By default this outputs a unified diff to stdout if any differences are found. While this is good information to have, it’s a really sucky way to display it — especially when we have tools like sdiff and vimdiff at our exposure.

sdiff simply takes the two input files and prints them out side by side with changes noted as characters in between the files. While this is much much better than the standard output of svn diff, vimdiff is still a better alternative because of it’s syntax highlighting.

vimdiff (or vim -d if you so choose) opens up vim in diff mode. This mode by default is two vertical split screens with one file in each screen. As usual, vim does some highlighting magic to make the output pretty and more meaningful. It also has a few commands to make your life easier when merging two versions of the same file (read up on do, dp, :diffget and :diffput).

Anyway, on to the point. To set up svn to use vimdiff as it’s default output you’ve got to do a few things. First, you need to create a wrapper around vimdiff. This is because of the way svn calls the diff utility, as far as I know there is no way around it. My vimdiff wrapper is below.

~/bin/svnvimdiff

exec /usr/bin/vimdiff ${6} ${7}

After that, you need to do one of two things:

  1. Create an alias that calls your vimdiff wrapper

    alias svndiff='svn --diff-cmd=/home/[username]/bin/svnvimdiff diff'

    OR

  2. Edit ~/.subversion/config to have the following lines

    [helpers]
diff-cmd = /home/[username]/bin/svnvimdiff

There is a third option, which is what I chose. I would not recommend it in most cases but I’m comfortable with how it works so I’ll post it anyway. In your shell config file (for me, .zshrc) add the following function.

svn()
{
  case "$1" in
  'diff')
    /usr/bin/svn --diff-cmd=$HOME/bin/svnvimdiff $@
    ;;
  'status')
    if [[ $PWD == $HOME ]]
    then
      /usr/bin/svn $@ | grep -v "^\?"
    else
      /usr/bin/svn $@
    fi
    ;;
  *)
    /usr/bin/svn $@
    ;;
  esac
}

This allows you to override the default svn binary to run however you’d like. In this example I set up vimdiff, as well as modify the output of svn status when I am in my home directory.

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