Syncs a fork with its parent repo (so you don't have to)

sync.sh

#!/usr/bin/env bash

# For best results, drop this into your path as "git-sync" and "chmod +x" it.
#
# From that point forward, you'll be able to use "git sync" as a command to
# synchronize any repository with a registered upstream.

set -eo pipefail

CURRENT_BRANCH=$(git status | grep '^On branch ' | sed 's/On branch //')

if [[ -n "$1" ]]; then
    TARGET_BRANCH="$1"
else
    TARGET_BRANCH=$CURRENT_BRANCH
    echo "No branch specified. Using current ($CURRENT_BRANCH)"
fi

if [[ ! $(git remote -v | grep 'upstream') ]]; then
    echo "No configured upstream repository. Use: git remote add upstream git@github.com:ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git"
    exit 1
fi

if [[ "$CURRENT_BRANCH" != "$TARGET_BRANCH" ]]; then
    git checkout "$TARGET_BRANCH"
fi

git fetch upstream

git merge "upstream/$TARGET_BRANCH"

git push