[WIP] CLI-227: add implicit context_mount to Image docker methods

[kramstrom]

Adds deprecation warning when using context_mount parameter on Image docker methods as part of the effort to remove mounts. This parameter which used to be necessary for COPY commands to work.

This PR instead creates an implicit context mount from the dockerfile/docker commands by parsing the COPY source patterns and use them as mount filters for the current directory.

Also adds support for finding a dockerignore file that matches the given dockerfile or if there's a generic one if using docker commands

[freider]

Haven't looked at the details too much, but looks good on the surface!

I just realized we might also want to (separately) add more fine grained control mechanisms/filter support to give people a way to exclude particular files they don't want to include (dockerignore style) before we can forcibly push people to use this.

As a start, maybe we could just start exposing condition in a more user-friendly way. Will discuss separately in slack

[freider]

Might want to add the ignore argument here as well if people want manual inline ignore patterns without external files, as a replacement for context_mount. And the pending deprecation could point people towards that argument

[freider]

(or dockerignore obviously)

[freider]

Wait, does dockerfile_commands support dockerignore with this? We only call find_dockerignore_file in from_dockerfile right? 🤔
No biggie if it doesn't - as long as we support ignore for now

[kramstrom]

added to dockerfile_commands as well -- currently both methods will try to find a dockerignore file unless a custom ignore argument is passed

[erikbern]

what's all this repr magic used for?

[kramstrom]

Moved the repr inside the class, but it's just a placeholder value for type hints & docs to make it simpler to understand what will happen if you don't pass in a custom ignore pattern-list or callable --> then we default to trying to find a matching dockerignore to your dockerfile (or just a generic one if you're using docker_commands) -- same as we have for add_local_python_source

[freider]

TLDR for why it's needed (this was my suggestion)

It's so that we can use these as default values in signatures and still emit valid python signatures in our type stubs, since things like inspect.signature(...) will just use the repr of all default values, and can't figure out stuff like import path of the specific constant we use as a default.

It's definitely a bit of a hack, but not something users should see. An alternative would be to do a bunch of ast magic to extract the signatures.