Make AllowedUsers configurable in sshd_config (#8094)

docker/root/usr/bin/entrypoint already allows for the specification
of USER, USER_UID, USER_GID. But since AllowedUsers is hardcoded in
sshd_config, one cannot log in as a user different ftom git.
This change substitutes ${USER} for git in the sshd_config template.

Signed-off-by: Jeronimo Pellegrini <j_p@aleph0.info>

docker/root/etc/templates/sshd_config

@@ -25,7 +25,7 @@ ChallengeResponseAuthentication no
 PasswordAuthentication no
 PermitEmptyPasswords no
 
-AllowUsers git
+AllowUsers ${USER}
 
 Banner none
 Subsystem sftp /usr/lib/ssh/sftp-server

docker/root/usr/bin/entrypoint

@@ -3,8 +3,6 @@
 if [ "${USER}" != "git" ]; then
     # rename user
     sed -i -e "s/^git\:/${USER}\:/g" /etc/passwd
-    # switch sshd config to different user
-    sed -i -e "s/AllowUsers git$/AllowUsers ${USER}/g" /etc/ssh/sshd_config
 fi
 
 if [ -z "${USER_GID}" ]; then