gl-auth-command: 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 CentOS possible default full paths are:

/usr/bin/gl-auth-command - from package: gitolite

You may install the required package with command yum install {package}

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