Consider a less ad-hoc approach to CLI arguments

[teodorlu]

Right now, we hand roll CLI arguments. We allow something like:

hotload PYTHON_MODULE_OR_SCRIPT [--entrypoint ENTRYPOINT_FUNCTION] [--recursive] [--no-clear]

But this isn't reflected in the helptext.

I know we have argparse -- but argparse can feel a bit heavy. I've used https://github.com/babashka/cli a bit recently, and I love how lightweight it is. Essentially, you specify the type of each option. The CLI lib can then return a map of all the options. Argparse might still be the way to go, not sure.

Current helptext output:

$ hotload
Running hotload ...
Usage: hotload SCRIPT
Hotload python script when files on standard input change

Example usage:

    find . -name '*.py' | hotload init.py

.py extension for script may be omitted.

[teodorlu]

A different CLI option:

hotload [OPTION...] [--] PYTHON_MODULE_OR_SCRIPT...

There's not really anything special with reloading one module.

---

Though perhap's it's normal? Use one python module as an entrypoint into your app, and consider other modules dependencies?

@tingstad's new feature of "also reload watched files if they are a module and have been changed since last time" is really something a bit different. It's an ergonomic solution if the user writes a main module and other modules.

[teodorlu]

Though. Do we actually need to change the CLI?

Real issues:

• Wrong helptext
• No CLI argument validation. For instance, bad input to --entrypoint will simply try, and crash if something goes wrong.

Hypothetical issues:

• We don't respond to hotload -h - in that case, hotload looks for a python file called -h.
• We don't support --entrypoint=PYTHON_FUNCTION
• We don't support short options

Perhaps trying to fix the real issues directly is better than redoing the whole CLI.

Potential new stuff:

• Allow disabling the "MODULE RELOADED" text
• Allow opting into "reload took x time" with CLI option

[teodorlu]

GNU CLI conventions: https://www.gnu.org/software/libc/manual/html_node/Argument-Syntax.html

[teodorlu]

Nice argparse guide: https://realpython.com/command-line-interfaces-python-argparse/