Dockerfile small refactor (#27757)

- Size and layer optimization,
- Maintaining consistency in definitions (comments, apk etc.),

docker/root/usr/bin/entrypoint

@@ -7,7 +7,7 @@ if [ ! -x /bin/sh ]; then
 fi
 
 if [ "${USER}" != "git" ]; then
-    # rename user
+    # Rename user
     sed -i -e "s/^git\:/${USER}\:/g" /etc/passwd
 fi
 
@@ -19,13 +19,13 @@ if [ -z "${USER_UID}" ]; then
   USER_UID="`id -u ${USER}`"
 fi
 
-## Change GID for USER?
+# 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?
+# 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