etckeeper_git_shell: 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/sbin/etckeeper_git_shell - from package: dms-dr

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