git-xbase: 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/share/git-cola/bin/git-xbase - from package: git-cola

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