Here are the relevant lines from my email generator script.  The script
greps to see if netdev is in the CC list but wireless isn't.  Then it
looks up the FIXES_HASH.  You have to have to have done a recent fetch
obviously.  My process doesn't work very well for patchsets.

regards,
dan carpenter

if grep -q netdev $MAIL_FILE && ! grep -q wireless $MAIL_FILE ; then
    if [ "$FIXES_COMMIT" != "" ] ; then
        if git merge-base --is-ancestor $FIXES_COMMIT net/main ; then
            TREE=" net"
        elif git merge-base --is-ancestor $FIXES_COMMIT net-next/main ; then
            TREE=" net-next"
        fi
    else
        TREE=" net-next"
    fi
fi

if [ "$TREE" == "" ] ; then
    if [ "$FIXES_COMMIT" != "" ] ; then
        if ! git merge-base --is-ancestor $FIXES_COMMIT origin/master ; then
            TREE=" next"
        fi
    fi
fi

git format-patch HEAD^ --stdout | sed -e "s/Subject: \[PATCH\]/Subject: [PATCH${TREE}]/" >> $MAIL_FILE