Add a manim cfg-show sub command

[leotrs]

With the new cascading config system, there will usually not be a single file that contains the final, actual, config that will be loaded into manim. It would be convenient to have a command, say manim cfg-show that parses the cascading files and then either (a) prints the final, actual, config options on screen, or (b) opens them as a new file.

Originally from here

I'm partial to (a) since (b) might give the false impression that one is editing "the" final config file. But there is no final config file, there are cascading files. In fact, running manim cfg-show from different folders will give different results since the config file with lowest priority is folder-wide.

Ties in with #151 @Aathish04 is there an issue for the general config-chooser command you are working on?

[XorUnison]

I would do it different. A final concatenated config showing option, and one opening the user configs should be clearly different options with different goals, so that'd be (a) and (b). So to clarify the (b) I'm talking about should just open and initialize the user config file, not show the concatenated final config.
So manim cfg-show and manim user-cfg-edit or something.

[Aathish04]

Ties in with #151 @Aathish04 is there an issue for the general config-chooser command you are working on?

@leotrs Considering that after #151, there'll be a few changes to how config works, I'll work on manim-cfg show after it's merged, if that's fine by you.

Can we keep manim-cfg as the base command and make everything config related subcommands of it?

manim-cfg write --user to write the config for the current user; manim-cfg write --cwd for the current working directory and so on.
manim-cfg show --user to show the config for the current user; manim-cfg show --cwd for the current working directory and so on.

We could have a manim-cfg export <output dir> to export the final config at the current working directory to another file at <output dir>, so on and so forth.

[leotrs]

@leotrs Considering that after #151, there'll be a few changes to how config works, I'll work on manim-cfg show after it's merged, if that's fine by you.

It will always be fine by me for you to take things off my plate ;)

Can we keep manim-cfg as the base command and make everything config related subcommands of it?

So argparse gives really convenient ways of using subcommands of the type manim cfg --some_flags. I'd rather keep everything under the same command (manim). For example, since we also want to support manim-ce, we would have to implement manim-ce-cfg as well. However, using the argparse system, we only need to implement the cfg subcommand once and it will work with both manim and manim-ce out of the box.

I like all of your ideas too. With the system I'm proposing, the specification might look like this:

manim cfg <action> --<level>

where is just a single CLI argument that has to be one of write, show, export, etc. Regardless of what the action is, the other argument can be one of user or cwd.

Ultimately, the actual final specification is up to y'all, but I do feel fairly strongly about using manim cfg as the subcommand instead of creating a new command manim-cfg. Open to discussion here, as always :)

[Aathish04]

@leotrs @XorUnison
Friendly reminder that I think I've addressed all your suggestions in #212 and that it's ready for review :)