Script to fetch all branches and fast forward merge master/main/develop without checkout

gf.sh

#!/bin/bash

#UPSTREAM=origin
UPSTREAM=upstream

function bexists() {
	local branch=${1}
	local existed_in_local=$(git branch --list ${branch})

	if [[ -z ${existed_in_local} ]]; then
		echo 0
	else
		echo 1
	fi
}

git fetch --all

for BRANCH in main master develop; do
	echo "Trying $BRANCH"
	if [[ $(bexists $BRANCH) -eq 1 ]]; then
		if [[ $(git rev-parse --abbrev-ref HEAD) == "$BRANCH" ]]; then
			echo "Merging $UPSTREAM/$BRANCH into the current branch"
			git merge --ff-only $UPSTREAM/$BRANCH
		else
			echo "Merging $UPSTREAM/$BRANCH into $BRANCH"
			git fetch $UPSTREAM $BRANCH:$BRANCH
		fi
	fi
done