[Mounts on images] add attach_local_file/attach_local_dir

[freider]

Since we create new methods we have the opportunity to introduce otherwise breaking logic changes for where to put/how to names files that have been somewhat inconsistent or poorly documented so far:

Here is the state of various edge case handling of directories and files copying:

Directories

shell

If you have a file source_dir/foo

cp -r source_dir /dest in shell creates a /dest/source_dir/foo

whereas adding a trailing slash on the source:

cp -r source_dir/ /dest in shell creates a /dest/foo

docker

In docker COPY source_dir /dest you always copy the content of the dir and never the dir itself (as if you always had a trailing slash in shell cp source dir).
If you want an output directory with the same name you specify that in the destination path explicitly.

current Modal Mount.from_local_dir

The current way this works in Modal mounts today and in attach_local_dir in this PR is how it works in Docker (always copy contents, never the directory itself).

current Modal image.copy_local_dir

Same as modal.mounts/docker - always copies content into the destination dir

Individual files

shell

cp some_file dest # this creates dest as a file
cp some_file dest/ # this creates dest/some_file and fails if dest doesn't exist

docker

COPY some_file dest # this creates dest as a file
COPY some_file dest/ # this creates dest/some_file and creates the dest dir if it doesn't exist

current Modal Mount.from_local_file

Mount.from_local_file("some_file") # this creates a file named "some_file"
Mount.from_local_file("some_file", remote_path="dest") # this creates a file named /dest
Mount.from_local_file("some_file", remote_path="dest/") # this creates a file named /dest 🤡 🤯

current Modal image.copy_local_file

Image.copy_local_file("some_file") # this creates a file named some_file in workdir
Image.copy_local_file("some_file", remote_path="dest") # this creates a file named dest in workdir
Image.copy_local_file("some_file", remote_path="dest/") # this creates the dest/ dir in workdir and creates a file dest/some_file 👍

Current differences compared to existing copy_ commands:

• Trailing slash on the remote_path of attach_local_file works the same regardless if we're using mounts or images
• The current copy_local_ commands support relative destination paths, but attach doesn't (this is fixable, but a bit messy, so I'm leaving it out for now and adding an exception so we can fix it later and people don't rely on the "broken" implementation)

Changelog

• Adds Image.attach_local_file(..., copy=False) and Image.attach_local_dir(..., copy=False) as a unified replacement for the old Image.copy_local_*() and Mount.add_local_* methods.