linux - How could I easily pack a directory to an ext4 loop partition image?

I would like to pack the content of a directory into an ext4 partition image easily, without mounting a loop device.

Background: I am building a version of Android which will mount system partitions as a loop device for ARM. Though I can create those partition images by hand using loop devices, it is very troublesome. I want to use an sh script to automatically do the work, and without needing to loop mount the dd-created image and use cp -rp. The best is to directly pack the files into an image file.

Question: Is there any simple command-line tools without needing loop mount and root permission that can pack files into an ext4 partition image?

Answer

In the Android build system there is a host binary make_ext4fs. You can create ext4 images by this way:

make_ext4fs [ -l  ] [ -j  ] [ -b  ]
    [ -g  ] [ -i  ] [ -I  ]
    [ -L  ] [ -f ] [ -a  ]
    [ -z | -s ] [ -J ]
     []