So I decided to streamline the process (based off this), so that the commit template that svn provides goes from:

--This line, and those below, will be ignored--

M    nearbygamers.com/public/stylesheets/screen.css

to:

--This line, and those below, will be ignored--

M    nearbygamers.com/public/stylesheets/screen.css

Index: foo
===================================================================
Index: public/stylesheets/screen.css
===================================================================
--- public/stylesheets/screen.css       (revision 360)
+++ public/stylesheets/screen.css       (working copy)
@@ -1,3 +1,6 @@
+h1 {
+  margin-bottom: 0.25em;
+}
 .tag_edit {
   margin-top: 2em;
   font-size: 80%;

First, I have a ~/bin for storing my own commands. In my .profile, I make sure this is the first thing in my path:

 
export PATH=~/bin:$PATH

Then I added a ~/bin/svn to catch commits, take a diff, and then call my . After saving and setting the execute bit (chmod +x ~/bin/svn), you’ll probably have to start a new shell for it to be called.

#!/bin/sh
REALSVN=/usr/bin/svn

ARGS="$@"

if [ "$1" = "commit" -o "$1" = "ci" ]; then
    shift # pop off $1 for diff
    TEMPLATE=`mktemp`
    $REALSVN diff "$@" > "$TEMPLATE"
    $REALSVN $ARGS --editor-cmd="~/bin/svn-diff-editor '$TEMPLATE'"
else
    $REALSVN $ARGS
fi

This called ~/bin/svn-diff-editor, which loads the diff into the commit template and invokes your default editor. (Don’t forget to set the execute bit on this as well.)

echo >> "$2"
cat "$1" >> "$2"
rm "$1"
$VISUAL "$2"