thg: 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/thg - from package: tortoisehg

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

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