[docker] drop the docker Makefile from the image (#6507)

docker/root/usr/bin/entrypoint

@@ -0,0 +1,37 @@
+#!/bin/sh
+
+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
+  USER_GID="`id -g ${USER}`"
+fi
+
+if [ -z "${USER_UID}" ]; then
+  USER_UID="`id -u ${USER}`"
+fi
+
+## Change GID for USER?
+if [ -n "${USER_GID}" ] && [ "${USER_GID}" != "`id -g ${USER}`" ]; then
+    sed -i -e "s/^${USER}:\([^:]*\):[0-9]*/${USER}:\1:${USER_GID}/" /etc/group
+    sed -i -e "s/^${USER}:\([^:]*\):\([0-9]*\):[0-9]*/${USER}:\1:\2:${USER_GID}/" /etc/passwd
+fi
+
+## Change UID for USER?
+if [ -n "${USER_UID}" ] && [ "${USER_UID}" != "`id -u ${USER}`" ]; then
+    sed -i -e "s/^${USER}:\([^:]*\):[0-9]*:\([0-9]*\)/${USER}:\1:${USER_UID}:\2/" /etc/passwd
+fi
+
+for FOLDER in /data/gitea/conf /data/gitea/log /data/git /data/ssh; do
+    mkdir -p ${FOLDER}
+done
+
+if [ $# -gt 0 ]; then
+    exec "$@"
+else
+    exec /bin/s6-svscan /etc/s6
+fi