This command will prefix xx commits number with [SYTO-640] including sqare brakets,
the importance of the \c
at the end of the prefix is to avoid new lines on the commit
otherwise this will transform the the commit name to commit description.
more info about \c
http://stackoverflow.com/questions/7154800/what-is-the-bash-escape-character-c
git filter-branch -f --msg-filter '
echo "[SYTO-640] \c" && cat
' HEAD~xx..HEAD