A shell script and alias to avoid making dumb mistakes with git-svn.

.gitconfig

[alias]
    ci = commit
    co = checkout
    st = status
    wdiff = diff --color-words
    svnci = !$HOME/src/dotfiles/git-svn-safe.sh dcommit
    svnre = !$HOME/src/dotfiles/git-svn-safe.sh rebase

git-svn-safe.sh

#!/usr/bin/env bash

branch=$(git symbolic-ref HEAD 2>/dev/null | cut -d"/" -f 3)

if [[ $branch = "master" ]]; then
    output=$(git svn "$@" 2>&1 | tee /dev/tty)

    count=$(echo -e "$output" | grep -c "^Committed")
    if [[ $count > 0 ]]; then
        echo -e "\nLog of $count commits:"
        git svn log --reverse --oneline -n"$count" | \
            sed -E 's/^(r[0-9]+) [|]/\1:/'
    fi
else
    echo Avoid runing git svn "$@" on a branch other than master.
fi

Consider this untested for platforms other than Mac OS 10.6.