Add check-features command

[koenw]

The check-features subcommand checks all Cargo.toml files in a given folder for dependencies that have default-features = false but are not part of the std feature.

This functionality was originally requested in Opstooling #55 and further discussed in Substrate #11715.

In order to facilitate these changes I've also updated the cargo_edit dependency.

[ggwpez]

Is there a reason for parsing Cargo.toml files instead of using cargo metadata? It outputs JSON and should also work for external dependencies:

"dependencies": [
{
  "name": "lazy_static",
  …
  "optional": true,
  "uses_default_features": true,
  "features": [],
  …
},
…

and then whether or not it is enabled in the features:

"features": {
  "default": [
    "heavyweight"
  ]

So it even tells you if the std feature exists for the dependency.

[koenw]

I guess that would work too, but I'm not working on this anymore so I haven't really thought about it.

[chevdor]

@koenw do you plan on keeping your work on this PR or shall we close it ?

[koenw]

@chevdor I do not plan to work on this PR, feel free to close.

[chevdor]

I still like the idea, we can reopen this later if bandwidth allows.