Script to merge a Gist fork into your original. You'll need the id of your Gist and the id of the fork.

gistmerge.sh

#!/bin/bash
# usage: ORIG=###### NEW=###### ./gistmerge.sh

# $ORIG = The Gist ID of your Gist
# $NEW = The Gist ID of the fork

# Note: chmod u+x gistmerge.sh may be necessary 
# if you're getting permissions errors

printf "\n\n... Cloning original Gist.\n\n"
git clone git@gist.github.com:$ORIG.git

cd $ORIG

printf "\n\n... Resetting the origin remote.\n\n"
# This is necessary because I have two GitHub accounts

git remote rm origin
git remote add origin git@github-ww:$ORIG.git

printf "\n\n... Adding remote for $NEW\n\n"
git remote add new git@gist.github.com:$NEW.git

printf "... Grabbing fork from $NEW\n\n"
git pull new master

printf "\n\n... Pushing changes to $ORIG\n\n"
git push

cd ..
printf "\n\n... Removing tmp folder\n\n"
rm -rf $ORIG

printf "..\n\n"
printf ".... Done\n\n"