A script to find the source branch for a branch in Git.

get_source_branch.sh

#!/bin/sh
# Script to find the parent branch for a given branch name
# If no branch name is specified, then it'll use the existing branch
# If you specify a branch to find the source of that doesn't exist, the script will exit with an error exit code

currentbranch=`git branch | grep '*' | sed 's/\* //'`
exists=`git show-ref refs/heads/$1`

if [ "$1" != "" ] && [ -z "$exists" ]; then
	echo "You've specified a branch that doesn't exist"
	exit 1
fi

if [ "$1" != "$currentbranch" ]; then
	git checkout $1 &> /dev/null
fi

git show-branch | grep '\*' | grep -v "`git rev-parse --abbrev-ref HEAD`" | head -n1 | sed 's/.*\[\(.*\)\].*/\1/' | sed 's/[\^~].*//'

if [ "$1" != "$currentbranch" ]; then
	git checkout $currentbranch &> /dev/null
fi