originally proposed here: moby/moby#28499 (comment)

after moby/moby#28499 gets merged, next step would to support file/dir permissions.

i'm proposing DEFATTR so that if you use multiple COPY or ADD you don't have to repeat the options:

DEFATTR chown=USER
DEFATTR chown=USER:GROUP
DEFATTR chown=UID
DEFATTR chown=UID:GID

chmod is a bit tricky because you definetely want different permissions for files and dirs:

DEFATTR chmod=a+rX
DEFATTR chmod=a+X

these would rise the x bit only if x bit is present for any of the users: chmod(1):

execute/search only if the file is a directory or already has execute permission for some user (X)

or more clearer directives for different kinds:

DEFATTR dir_chmod=0755 file_chmod=0644