prepare-commit-msg.inbash

#!/bin/bash
branchPath=$(git symbolic-ref -q HEAD) #Somthing like refs/heads/myBranchName
branchName=${branchPath##*/}      #Get text behind the last / of the branch path

firstLine=$(head -n1 $1)

if [ -z "$firstLine"  ] ;then #Check that this is not an amend by checking that the first line is empty
    sed -i "1s/^/[$branchName] \n/" $1 #Insert branch name at the start of the commit message file
fi