fastforward: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/fastforward - from package: fastforward
/var/lib/qmail/bin/fastforward - from package: fastforward

You may install the required package with command apt-get install {package}

Error in other languages:
fastforward: bevel nie gevind nie
fastforward: comandă negăsită
fastforward: comando não encontrado
fastforward: commande introuvable
fastforward: command not found
fastforward: käsku ei ole
fastforward: không tìm thấy lệnh
fastforward: komanda nerasta
fastforward: Kommando nicht gefunden.
fastforward: kommandot finns inte
fastforward: komut yok
fastforward: nie znaleziono polecenia
fastforward: níor aimsíodh an t-ordú
fastforward: no se encontró la orden
fastforward: no s'ha trobat l'ordre
fastforward: opdracht niet gevonden
fastforward: parancs nem található
fastforward: perintah tidak ditemukan
fastforward: príkaz nenájdený
fastforward: příkaz nenalezen
fastforward: команда не найдена
fastforward: командата не е открита
fastforward: 命令找不到
fastforward: コマンドが見つかりません