Fast forward a local branch to a remote branch The local branch doesn't have to be checked out. Links: http://stackoverflow.com/a/4157435/860556 http://stackoverflow.com/questions/5167957/is-there-a-better-way-to-find-out-if-a-local-git-branch-exists http://stackoverflow.com/questions/3216360/git-update-a-local-branch-without-checking-it-out

git-ff-update.sh

#!/bin/bash -e

# DECLARE FUNCTIONS

# branch_exists_local <branch>
function branch_exists_local {
	git show-ref --verify --quiet "refs/heads/$1"
}

# branch_exists_remote <remote_branch>
#   where <remote_branch> is in form: "remote/branch"
function branch_exists_remote {
	git show-ref --verify --quiet "refs/remotes/$1"
}

function is_fast_forward {
	if [[ `git merge-base $1 $2` = `git rev-parse $1` ]]; then
		return 0;
	else
		return 1;
	fi;
}

# PARSE INPUT ARGUMENTS

BRANCH=$1

if [[ -z $BRANCH ]]; then
	echo No branch specified
	exit 1
fi

if [[ -z "$2" ]]; then
	REMOTE="origin/$BRANCH"
else
	REMOTE=$2
fi

# RUN

if ! branch_exists_local $BRANCH; then
	echo "Local branch $BRANCH doesn't exist!"
	exit 1;
fi

if ! branch_exists_remote $REMOTE; then
	echo "Remote branch $REMOTE doesn't exist!"
	exit 1;
fi

if is_fast_forward $BRANCH $REMOTE; then
	git branch -f $BRANCH $REMOTE
	echo Fast-forward update performed - $BRANCH is now on $REMOTE
else
	echo Cannot update $BRANCH using $REMOTE - non-fast-forward update
	exit 1
fi