stg-cvs: command not found

Have You tried accessing the binary with the full path?

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/stg-cvs - from package: stgit-contrib

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