Command line arguments handling and --help

[mati865]

Are there any concrete plans for CLI and --help?
Some tools rely on linker's --help to find out what is implemented.

I'll split the discussion into the separate topics ideas below, feel free to edit the comments.

[mati865]

Keep current arguments parsing and maintain corresponding output for --help manually.

Pros:

• Argument parsing is simple and easy to work with
• Low cost of the introduction (parsing is already implemented)

Cons:

• --help has to be maintained by hand

[mati865]

Port to Clap.

Pros:

• --help is auto-generated

Cons:

• Requires getting used to
• Is known to negatively affect build time

[mati865]

Some other crate?

[davidlattimore]

I'm not too concerned about the build time for clap, since linker-diff, which is part of the wild repo already pulls it in. More of a concern is whether it's flexible enough to parse the arguments in a way that's compatible with what GNU ld, lld etc do, since we need to be a drop in replacement for them.

One of the more tricky things is pushing and popping of state. Filenames and some other arguments like -l then need to have the current state associated with them.

There's also other little things like accepting either single or double dashes for long form arguments.

I haven't had a good look at clap to see if it provides all the required flexibility. If it has hooks that can be run each time a certain argument is encountered then maybe it might be possible.

[mati865]

Good point, I forgot about single dash arguments.
Uuitls has a similar issue: uutils/coreutils#4254, but it's a low priority on the Clap side: clap-rs/clap#2468
One way around could be to convert single dash arguments into double dash arguments before feeding them to Clap, but this feels hacky and --help would show them as double dashed.

I had never paid much attention to {push,pop}-state, but now that I learned how it works, I see the problem. I don't think this is solvable with Clap.