Overlay's files on an existing path, overwriting anything that it finds.

overlay-dir.py

#!/usr/bin/env python
# A Python function for overlaying a source directory on top of a destination dir

import os
import shutil
import re

def normalize_paths(dest_prefix, src, dest):
    dest = re.sub(r'^/+', '', dest)
    return (
        os.path.abspath(src),
        os.path.join(dest_prefix, dest)
    )

def overlay(dest_prefix, src, dest):
    abs_src, abs_dest = normalize_paths(dest_prefix, src, dest)
    if os.path.isfile(abs_src):
        return overlay_file(abs_src, abs_dest)
    elif os.path.isdir(abs_src):
        return overlay_dir(abs_src, abs_dest)

def overlay_file(src_file, dest):
    if dest.endswith('/'):
        dest_file=os.path.join(dest,os.path.basename(src_file))
    else:
        dest_file = dest
    dest_dir = os.path.dirname(dest_file)
    if not os.path.exists(dest_dir):
        os.makedirs(dest_dir)

    print("{} -> {}".format(src_file, dest_file))
    shutil.copy2(src_file, dest_file)

def overlay_dir(abs_src, abs_dest):
    for root, dirs, files in os.walk(abs_src):
        dest_root=os.path.normpath(root.replace(abs_src, abs_dest))
        if not os.path.exists(dest_root):
            os.mkdir(dest_root)
        for f in files:
            src_file=os.path.join(root, f)
            dest_file=os.path.join(dest_root, f)

            print("{} -> {}".format(src_file, dest_file))
            shutil.copy2(src_file, dest_file)

if __name__ == "__main__":
    # The conda-build dir is spatted to PREFIX/
    # overlay("/tmp/tmp0", "/Users/sodre/git/conda/conda-build", "/")

    # The overlay-dir.py file is copied to PREFIX/overlay-dir.py
    overlay("/tmp/tmp1", 'overlay-dir.py', '/')

    # The overlay-dir.py file is copied to PREFIX/bin/overlay-dir.py
    overlay("/tmp/tmp2", 'overlay-dir.py', '/bin/')

    # The overlay-dir.py file is copied to PREFIX/bin/overlay
    overlay("/tmp/tmp3", 'overlay-dir.py', '/bin/overlay')