Create the parent directory of the home directory before calling mkho…

…medir_helper

The tool fails with exit code 6 if the top-level directory does not exist yet.

    (a39bc32231c8)root@c71fe951b480:/# getent passwd johannes
    johannes:x:1000006:1000:Johannes Meyer:/share/homes/johannes:/bin/bash
    (a39bc32231c8)root@a39bc32231c8:/# rm share -R
    (a39bc32231c8)root@a39bc32231c8:/# mkhomedir_helper johannes; echo $?
    6
    (a39bc32231c8)root@a39bc32231c8:/# mkdir share
    (a39bc32231c8)root@a39bc32231c8:/# mkhomedir_helper johannes; echo $?
    0

src/rocker/templates/user_snippet.Dockerfile.em

@@ -19,7 +19,7 @@ RUN existing_user_by_uid=`getent passwd "@(uid)" | cut -f1 -d: || true` && \
 
 @[if not home_extension_active ]@
 # Making sure a home directory exists if we haven't mounted the user's home directory explicitly
-RUN mkhomedir_helper @(name)
+RUN mkdir -p "$(dirname "@(dir)")" && mkhomedir_helper @(name)
 @[end if]@
 # Commands below run as the developer user
 USER @(name)